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DEPARTMENT OF THE INTERIOR 

UNITED STATES GEOLOGICAL SURVEY 

v> ' ‘‘ i T « 

GEORGE OTIS SMITH, Director 


Bulletin 580—M 


THE ROCHESTER MINING DISTRICT 

NEVADA 


BY 

FRANK C. SCHRADER 


CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I—M 


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WASHINGTON 

GOVERNMENT PRINTING OFF IC E 

1914 








d; of n, 

MAY 20 1915 






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CONTENTS. 



T> 


V 


Pase. 


Introduction. 325 

Surface features. 325 

History, production, and mining operations. 326 

Geology. 331 

Rocks of the region. 331 

General features. 331 

Koipato formation. 331 

'Star Peak formation. 332 

Valley fill. 333 

Structure. 333 

Rocks of the Rochester district. 334 

Ore deposits. 338 

Lodes. 338 

General features. 338 

Nenzel Hill belt. 342 

Nenzel Hill ore deposits. 342 

Mining development. 343 

Source of the Nenzel Hill ore deposits. 350 

Packard ore deposits. 350 

Lincoln Hill belt. 354 

General features. 354 

Lincoln Hill deposits. 354 

Source of the Lincoln Hill ore deposits. 356 

Deposits in neighboring localities. 358 

Mcllravy prospect. 358 

Lee-Stuart mine. 358 

Cole prospect. 360 

Dixie mine. 360 

Nevada Almaden prospect. 361 

Butte prospect. 361 

McNickle prospect. 361 

Relief mine. 362 

Deposits in Pole Canyon. 364 

Age of deposits of the Rochester district. 367 

Future of the district. 368 

Placers. *368 

American Canyon. 368 

Walker Gulch. 368 

Spring Valley. 370 

Rochester Canyon. 370 

Weaver Canyon. 371 

South American Canyon. 371 

Limerick Canyon. 371 


in 














































ILLUSTRATIONS. 




Plate YIII. 
Figure 89. 

90. 

91. 

92. 


Geologic map of the Rochester district, Nev. 

Silicified croppings and mines on Nenzel Hill, Rochester district, 

Nev., looking east-northeast.. 

Diagrammatic cross section of Packard Ridge, Rochester district, 
Nev., showing position of the principal ore deposits and proba¬ 
ble course of the solutions by which the ore was deposited.... 
Plan of the principal lodes and veins in Nenzel Hill, Rochester 

district, Nev. 

Plan and geologic relations of the principal veins in the Pole Can¬ 
yon district, Nev. 

IV 


Page. 

334 

329 

335 
343 
365 







THE ROCHESTER MINING DISTRICT. NEVADA. 


By Frank C. Schrader. 


INTRODUCTION. 

This report is based on a two weeks’ visit made to the Rochester 
district and vicinity by the writer in May, 1913. A brief prelimi¬ 
nary statement of the results of the reconnaissance was given to the 
press by the Survey in June, 1913. 

Information generously given by mining companies, prospectors, 
engineers, and surveyors operating in the district has been of ma¬ 
terial aid in the preparation of this report. 

The Rochester district, comprising about 25 square miles, is in 
west-central Nevada, in the southern part of Humboldt County. It 
is 9 miles southeast of Nixon, formerly Oreana, on the main line of 
the Southern Pacific Railroad, and 20 miles northeast of the town 
of Lovelocks. With both of these places it has daily freight, ex¬ 
press, passenger, and mail service. A private branch railroad, the 
Nevada Short Line, extends from Nixon 5 miles across the lowland 
to the edge of the district. 

The mining settlement of Fitting, formerly Spring Valley, lies a 
few miles to the northeast. South of Fitting, heading almost in the 
heart of the Rochester district, is American Canyon, noted for its 
large production of placer gold. The eastern part of the Rochester 
district was formerly known as the Sacramento district. 

SURFACE FEATURES. 

The Rochester district lies in the Humboldt Range, which is 
separated from the Montezuma or Trinity Mountains by the Hum¬ 
boldt Valley on the west, and from the Pahute Range by the Buena 
Vista Valley on the east. Most of these valleys, which are 8 to 10 
miles wide, are of the flat-bottomed infilled Great Basin type. 

The Plumboldt Range, also called the Koipato Range in the re¬ 
ports of the Fortieth Parallel Survey, 1 is about 75 miles long and 
culminates on the north in Star Peak, 10,000 feet above sea level. 

Near its middle point, in the latitude of Nixon and Rochester, 
the range is traversed by a low pass known as Cole Canyon (PI. 

1 Hague, Arnold, and Emmons, S. F., Descriptive geology : U. S. Geol. Expl. 40th Par., 
vol. 2, p. 713, 1877. 


325 







326 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

VIII), which divides it into two parts. The northern part, which 
has a northerly trend, Louderback 1 calls the Star Peak Range, and 
the southern part, which has a northeasterly trend, he calls the Hum¬ 
boldt Lake Range. 

The Star Peak Range, in which the Rochester district lies, is 
fairly uniform in outline and has an average width of about 10 miles, 
its maximum width, which is about 15 miles, being in its southern 
part. Buffalo Peak, a huge mass nearly 8,400 feet in elevation, forms 
its southern end. The lowest pass in the range is Spring Valley 
Pass, 6,250 feet in elevation, or nearly 2,000 feet above the adjoining 
Humboldt Valley on the west. 

The range is described by Hague 2 as a simple ridge with the axis 
near the center of the uplift, from which numerous canyons with 
broad basin-like heads, abruptly becoming narrower as they descend, 
extend down the mountain slopes at regular intervals. This descrip¬ 
tion applies particularly to the Rochester district, where the heads 
of the lateral canyons almost coalesce. 

The Rochester district lies in the southern part of the Star Peak 
Range, chiefly on its upper west slope, at elevations between 4,000 
and 7,500 feet, as shown on the accompanying map (PI. VIII). 
The area is mountainous but not rugged. Many of the canyons and 
ravines are passable for wagons, and most of them contain springs 
and wells of potable water. 

The western part of the area is drained chiefly by Packard, 
Weaver, Rochester, Limerick, and Sacramento canyons, which enter 
Humboldt Valley, and Cole Canyon. The eastern part of the area 
is drained by Buffalo, South American, and American canyons and 
by Spring Valley, all of which open into Buena Vista Valley. 

Within the district the crest of the range is represented by a 
relatively narrow ridge, about 6,600 feet in elevation. Its dominant 
feature is Nenzel Hill, an oval silicified knob, 3,000 feet long by 2,000 
feet wide, at the head of Rochester and South American canyons. 
This hill rises 7,300 feet above sea level, or 500 feet above the adjoin¬ 
ing portions of the divide. Lincoln Hill, a prominent landmark, 
which forms the end of the ridge bounding Rochester Canyon on 
the north, about 2f miles w T est of Nenzel Hill, rises to an elevation of 
6,600 feet. 

HISTORY, PRODUCTION, AND MINING OPERATIONS. 

The presence of mineral deposits in the Humboldt Range and the 
Rochester region was known half a century ago. Mining began in 
this part of Nevada about the year 1860 with the organization of 

1 Louderback, G. D., Basin range structure of the Humboldt region : Geol. Soc. America 
Bull., vol. 15, p. 294, 1904. 

2 Hague, Arnold, and Emmons, S. F., op. cit., p. 713. 



ROCHESTER MINING DISTRICT, NEV. 


327 


the Humboldt district, on the northwest slope of Star Peak. 1 The 
Star Peak and Buena Vista districts were organized in 1861. 2 

Rochester Canyon took its name from some pioneers who in travel¬ 
ing overland from Rochester, N. Y., in the early sixties, prospected 
and mined at its mouth and are said to have examined most of the 
Humboldt Range from this locality southward. Some of the party 
worked the Montana lode in 1867, but soon after ceased operations. 
Supplies in those days were hauled overland from Sacramento and 
the rich ore was shipped by way of San Francisco to Swansea, Wales. 

Evidences of former work in this district are the old Montana shaft 
near Lincoln Hill, sunk in the early sixties, and the Oro Fino shaft, 
in Gold Ridge, to the north (PI. VIII). Rich float is said to have 
been discovered at Lincoln Hill by Tooper Bennett in 1888. 

The first successful lead-silver smelter in Nevada was built and 
operated on Humboldt River just below Oreana to treat ore from the 
Montezuma mine, in the Trinity district. 2 

The discovery of ore in Nenzel Hill, the center of the present 
activity, was made a decade or more ago by Charles E. Stevens, a 
pioneer. Little work, however, was done at that time, and the ground 
reverted to the Government. 

Later, in 1909, Joseph Nenzel and others relocated the ground, 
and a small shipment of ore was made in August, 1912, partly from 
the Causten tunnel, but mainly from talus or float. Large bodies of 
$50 to $60 ore were found in November, 1912, and in February and 
March, 1913, other bodies were opened in a second vein, at a depth 
of 130 feet. A carload and several smaller consignments of the rela¬ 
tively high-grade ore were shipped about Christmas, 1913, by Nenzel 
from the Causten, and by Frank Schick and Walt Moynaugh from 
the Weaver No. 2 claim. These shipments attracted attention to 
Rochester and the district was soon after visited by half a score of 
able mining engineers, nearly all of whom reported on it favorably. 

In less than a month the hitherto desolate canyon had a population 
of more than 2,000 people and contained many substantial two-story 
buildings. Three town sites, Rochester (or Lower Town), Central 
Rochester, and East Rochester, were laid out, but these soon coalesced 
along a main street, 2J miles in length, extending from Lincoln Hill 
to the base of Nenzel Hill. East Rochester, near the head of the can¬ 
yon, at an elevation of 6,200 feet, soon became and has continued to 
be the principal camp. 

Blocks 300 by 600 feet in area were leased and actively worked by 
experienced mining men and at the time of the writer’s visit, in May, 

1 Hague, J. D., Mining industry : U. S. Geol. Expl. 40th Par., vol. 3, p. 310, 1870. 

2 Ransome, F. L., Notes on some mining districts in Humboldt County, Nev. : U. S. Geol. 
Survey Bull. 414, p. 10, 1909. 





328 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

1913, the development of the mines and the showing of ore made 
without aid of outside capital were remarkable. Ground was opened 
under six or eight leases to a depth of 130 feet by crosscut tunnels 
from 100 to 300 feet in length. About 2,000 tons of ore, averaging 
approximately $30 to the ton, had been mined and shipped, and much 
more, 100,000 tons it was said, was in sight. Nearly a score of prop¬ 
erties were producing. 

From March to November, 1913, inclusive, the known shipments 
from the district amounted to approximately 14,000 tons of ore 
having a total value of about $415,000, and the production for the 
year 1913 was approximately $500,000. In addition much milling 
ore had accumulated on the dumps. Of the ore shipped, 12,740 
tons came from Nenzel Hill, chiefly from the Big Four, Codd, and 
Colligan leases, and averaged approximately $28 to the ton; 1,120 
tons, averaging $50 to the ton, came from Packard; and 120 tons, 
which averaged $79 to the ton, came from the Buck and Charley 
lease, opposite Lincoln Hill. Some ore was produced also by Lin¬ 
coln Hill and by the Limerick and Sunflower groups at the head of 
Rochester Canyon. The total production to September, 1914, is 
reported to be more than $1,200,000. In addition it is estimated 
that there had been developed in the district by that date more than 
100,000 tons of milling ore, of which the Codd lease is credited with 
50,000 tons averaging from $10 to $20 to the ton, the Four J lease 
with 20,000 tons, and the Rochester-Weaver mine with 15,000 tons. 
The average value of the ore produced during the 18 months ending 
June 30, 1913, is about $25 to the ton. Most of the ore mined has 
been sent to the Wabuska and Salt Lake smelters, although some 
was shipped to the Western Ore Purchasing Co., at Goldfield. 

By December, 1913, development on most of the principal leases 
had extended to depths of about 300 feet, and the Causten tunnel, 
630 feet in length, had reached a depth of 400 feet. 

Two companies, the Rochester Mines Co- and the Rochester- 
Weaver Mining Co., own most of the developed ground on Nenzel 
Hill. According to the first annual reports of these companies, 
there was shipped during the year 1913 from the Rochester Mines 
Co.’s ground 14,726 tons of ore, averaging $25.04 to the ton, worth 
$368,770, the net profit being about $19,192, and from the Rochester- 
Weaver Mining Co.’s ground 953 tons, averaging $31.74 to the ton, 
worth $30,254.30. 

At first the ore was chuted in sacks several hundred feet down the 
steep side of Nenzel Hill, thence stone-boated nearly a half mile 
farther to the head of the wagon road in Rochester Canyon, down 
which it was freighted to Nixon. Early in the spring of 1913, how¬ 
ever, 6 miles of road of easy grade, suitable for auto trucks, was con¬ 
structed jointly by the Rochester Mines Co. and the lessees, at a cost of 


ROCHESTER MINING DISTRICT, NEV. 


329 


$10,000. This road, as shown on the map (PL VIII), extends up 
Limerick Canyon directly to the mines, almost to the top of Nenzel 
Hill (fig. 89). It enabled a saving of about $1 a ton haulage on 
the ore shipped during the year. Early in the summer it was con¬ 
nected at the mouth of the canyon with the new 5-mile branch rail¬ 
road (the Nevada Short Line), built from Nixon across the soft 
lowland by the Rochester Hills Mining Co. 

The railroad is now being extended up Rochester Canyon and 
will be operated as a common carrier. This road will greatly reduce 
the cost of ore shipment and freight. * Arrangements will be made 
whereby trains will be run directly to the mines near the summit of 



Figure 89.—Silicified croppings and mines on Nenzel Hill, Rochester district, Nev., looking 

east-northeast. 

Nenzel Hill. Under present conditions ore worth less than $22 to 
the ton can not be shipped with profit. 

In 1913 the production was nearly all made by lessees. The lessee 
system has proved very satisfactory to all concerned, and probably 
about twice as much development has been made thus as would have 
been made by the owning companies themselves in the same length 
of time. With the expiration of the leases, however, the companies 
mostly plan to operate the Nenzel Hill mines themselves. A con¬ 
solidation of the five or six principal properties is under considera¬ 
tion, as the relations of the ore bodies and the topography of the hill 
are admirably adapted to work under one management. 

According to the report of the Rochester Mines Co. for 1913, the 
proceeds from each ton of ore were apportioned as follows: 


Wagon haulage_$4. 43 

Railroad freight and treatment_ 8. 70 

Lessees’ share_ 9.79 

Company’s royalty- 2.12 
















330 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

A very complete 100-ton cyanide plant is now being built, at a cost 
of $100,000, by the newly organized Rochester Consolidated Mining 
& Milling Co. The plant is located in the southeastern part of the 
district, in Rochester Canyon, near the Rochester and Packard road 
forks, on the railroad, about half a mile below Lower Town. At 
the outset ore from the Nenzel Hill mines will be delivered at the 
plant by a 2-mile aerial tram. 

In this plant a Blake crusher, a 10-stamp mill, and tube mills will 
be used for crushing. The plant, although primarily intended for 
treating ore from the Rochester mines group, will also do custom 
work for the various mines of the district, which will make the large 
reserves of milling ore accumulated in the district available for treat¬ 
ment. The plant is expected to be in operation by January 1, 1915. 
Water for the plant is to be brought by pipe line from Hardesty 
Canyon, 5 miles distant, near Packard. The machinery is to be 
driven by hydroelectric power supplied from the Lahontan dam. 

Shipment mill tests made of the ores to be treated by the process 
to be here used are said to indicate a recovery of about 95 per cent of 
the silver and 92 per cent of the gold from the sulphide ores and 
85 per cent of the silver and 90 per cent of the gold from the oxidized 
ores. From the 200-foot level down the ores are said to be nearly all 
sulphide. 

In April, 1914, the camp was shipping 130 to 150 tons of ore a day, 
about 40 tons of which was being shipped by the Rochester Hills 
Mining Co. In May there was reported to be in sight on the dumps 
and blocked out at the Nenzel Hill mines 100,000 tons of ore averag¬ 
ing $15 to the ton, or about $1,500,000 worth of good milling-grade 
ore. For each ton of shipping ore taken out about 4 tons of low- 
grade or $15 milling ore is developed. The Nenzel Hill ore, it is 
estimated, can be mined for about $3 a ton and milled at a cost of 
about $6 a ton. 

Ample water for milling and domestic use can be brought by 
gravity, it is said, from Lee Springs, a few miles to the north. At 
the time of the writer’s visit sufficient water could also be pumped 
from the basin at the east base of Nenzel Hill, where several strong 
springs issue into South American Canyon. This water apparently 
owes its source largely to the easterly dip of the rocks in the adjoin¬ 
ing axis of the range. The quantity stored here that could be relied 
on in the dry season depends mainly on the volume of the alluvial 
deposits, which fill the basin and seem to have considerable thickness. 
Springs occur also in the neighboring American, Limerick, and 
Weaver canyons. Thus far the water supply for Rochester has 
been obtained from wells 10 to 40 feet deep sunk in the alluvial 
gravels of Rochester Canyon. The supply for Packard is drawn 


ROCHESTER MINING DISTRICT, NEV. 


331 


from Black Knob Spring, about a mile and a half away, in Cole 
Canyon (PI. VIII). 

The climate of Rochester is ideal in summer, but the winters are 
severe for Nevada. The hills are generally free of snow in early 
April. High winds are common, as are also thunderstorms or 
cloudbursts, which late in May, 1913, flooded the canyons with short¬ 
lived torrents. 

Grass and scattered trees of the western juniper grow on the 
hillsides. 

At the time of the writer’s visit, in May, 1913, the district had a 
population of about 1,000 people, of whom 700 were in East Roch¬ 
ester, where 200 miners were at work in Nenzel Hill and 250 were in 
Lower Town, and Packard, the newest settlement, only a few weeks 
old, at the south base of Packard Hill, had a population of about 
100, which was daily increasing. Panama, on the northeast near 
Spring Valley Pass, in the head of Limerick Canyon, a mile and 
a half over the ridge from Rochester, contained a score of people. 

Nixon, formerly little more than a watering station in the desert 
for Southern Pacific trains, had become a small town. 

GEOLOGY. 

BOCKS OF THE BEGION. 

GENERAL FEATURES. 

Hague 1 described the Humboldt Range as consisting of an Archean 
nucleus, surrounded and unconformably overlain by Triassic strata 
of great thickness, these in turn being overlain by Jurassic beds, 
which, along the base of the range and locally elsewhere, are steeply 
tilted, broken, and associated with masses of Tertiary rhyolite and 
basalt, and with poorly exposed Miocene beds called the Truckee 
group. The Archean and Triassic rocks were described as sparingly 
cut by Mesozoic dikes, chiefly diabase. The Triassic rocks were 
separated by Hague into two groups, which in ascending order he 
designated the Koipato and Star Peak “ series,” but which are here 
termed formations. 

KOIPATO FORMATION. 

The Koipato formation, so called from the Indian name of the 
Humboldt Range, occupies, according to the map of the Fortieth 
Parallel Survey, approximately the north half of the southern half 
of the Star Peak Range, including the Rochester district. It forms 
a belt 8 miles wide, trending from Cole Canyon diagonally north- 


1 Hague, Arnold, and Emmons, S. F., op. cit., p. 714. 



332 CONTRIBUTIONS TO ECONOMIC GEOLOGY , 1913, PART I. 

eastward across the range to Union ville, whence, as a narrow strip, 
the formation is shown as extending 9 miles northward along the 
east base of the range. Similarly, along the west base, a narrow 
tongue of the Star Peak formation is mapped as extending south¬ 
ward to Sacramento Canyon. 

The Ivoipato formation w-as supposed by Hague to consist chiefly 
of metamorphosed silicified sedimentary rocks, beds of quartzite 
overlain by interstratified beds of limestone, quartzite, and “ felsitic 
porphyroids.” It was referred to the Triassic and regarded as of 
the same geologic age as the low T er members of the “ Red Beds ” of 
the Rocky Mountain region. Its thickness was estimated at 6.000 
feet. 

STAR PEAK FORMATION. 

In or near the Rochester district the Star Peak formation suc¬ 
ceeds the Koipato formation on the southeast. It occupies mainly 
the southern fourth and the northern half of the Star Peak Rans:e. 
Its thickness was estimated by Hague at 10,000 feet. 

According to the section compiled by Ransome 1 from Hague’s 
description it consists of the following members: 

Section of the Star Peak formation, Star Peak Range, Nev. 

[Compiled from the description by Arnold Hague.] 


Feet. 

Quartzite and overlying limestone_ 4, 000-5, 000 

Massive limestone_ 1, 800-2, 000 

Black arenaceous slates_ 200- 300 

Slaty quartzites alternating with greenish schistose 

rocks- 1, 500 

Limestones, dark, almost black at the base, passing 

up into gray and blue varieties_ 1,200-1.500 

Ransome 2 also writes: 


The Star Peak formation is noted for its abundant Middle Triassic vertebrate 
and invertebrate fossils, which have been described by Gabb, 3 Meek, 4 Hyatt and 
Smith, 5 and J. C. Merriam. 6 * * * Hyatt and Smith 7 [and Smith 8 ] state 

that the Upper Triassic is also represented in the Humboldt Range, and list 
half a dozen fossils. The beds containing them are said to be unconformably 
overlain by limestone containing Jurassic forms. 


1 Ransome, F. L., op. cit., p. 31. 

2 Idem, p. 32. 

3 Gabb, W. M., Paleontology : California Geol. Survey, vol. 1, pp. 19-35, 1864. 

4 Meek, F. B., Paleontology : U. S. Geol. Expl. 40th Par., vol. 4, pt. 1, pp. 99-129 Pis 
X and XI, 1877. 

5 Hyatt, Alpheus, and Smith, J. P., The Triassic cephalopod genera of America : U. S. 
Geol. Survey Prof. Taper 40, pp. 21-23, Pis. XXII-XXV, 1905. 

0 Merriam, J. C., Triassic Ichthyosauria : California Univ. Mem., vol. 1, No. 1 pp. 18-19 
1908. 

7 Hyatt, Alpheus, and Smith, J. P., op. cit., p. 26. 

8 Smith, .1. P., The Middle Triassic marine invertebrate faunas of North America: U. S. 
Geol. Survey Prof. Paper 83, 1914. 








ROCHESTER MINING DISTRICT, NEV. 


333 


Later and more detailed work than that of the Fortieth Parallel 
Survey has shed more light on the geology of the range and led to 
certain revisions in the interpretation of the geologic phenomena 
and classification of the rocks. Of these revisions the following are 
the more important: 

According to Louderback, 1 the supposed Archean nucleus exposed 
in Pocky Canyon, 7 miles north of Nixon, is post-Triassic intrusive 
granite with associated contact-metamorphic phenomena in both the 
granite and the host rocks. * 

According to Pansome, 2 the Koipato formation as a whole is a 
volcanic complex, consisting chiefly of rhyolitic flows, in which non- 
volcanic sediments, including limestones, form only a subordinate 
part. With this view, the determinations of the rocks in the 
Pochester district by Jones 3 and others, including the present 
writer, are essentially in accord. 

The boundary between the Koipato and Star Peak formations, 
which is erroneously represented on the Fortieth Parallel Survey 
map as passing through Nenzel Hill, apparently lies well to the east 
of Nenzel Hill and of the area shown on the accompanying map (PI. 
VIII), but, as Pansome has pointed out, the place of division between 
the two formations lacks accurate definition. On the northeast the 
rhyolites of the Koipato formation and of Nenzel Hill extend about 
a mile and a quarter down American Canyon to the 5,740-foot con¬ 
tour, where they are succeeded by greenstone and sedimentary rocks 
apparently belonging to the Star Peak formation. Approximately 
the same is true of their extension down South American Canyon, 
on the east, and into the mountains forming the crest of the range, on 
the southeast. 

VALLEY FILL. 

The, intermontane valley fill, particularly that between the mouth 
of Rochester Canyon and the railroad west of it, consists chiefly of 
the deposits of the Quaternary Lake Lahontan, in large part overlain 
by recent alluvium, talus, and debris washed from the neighboring 
mountains. As seen at Nixon and elsewhere, the lake beds consist 
chiefly of very fine, soft silts, over which freighting by team is 
difficult and expensive. 

STRUCTURE. 

The general structure of the Star Peak Range is described by 
Hague 4 as that of an anticlinal fold extending diagonally across 

1 Louderback, G. D., op. cit., pp. 317—318. 

2 Ransome, F. L., loc. cit. 

3 Jones, J. C., Geology of Rochester, Nev.: Min. and Sci. Press, vol. 106, pp. 737-738, 
1913. 

4 Hague, Arnold, and Emmons, S. F., op. cit., pp. 716, 728. 




334 CONTRIBUTIONS TO ECONOMIC GEOLOGY , 1913, PART I. 

the topographic uplift, striking about N. 30° E. and crossing the 
range obliquely at Spring Valley Pass. 

In a broad way this anticlinal structure appears to extend, so far 
as the present writer’s observations show, through the southern part 
of the range. 

Louderback 1 regards the Star Peak Range as an elevated and 
eastward-tilted fault block of pre-Cretaceous rocks similar to the 
Humboldt Lake Range, which he has carefully studied. The main 
fault along the west base of the range is regarded by him as the 
same as that which, extending through Cole Canyon, separates the 
Star Peak and Humboldt ranges. 

ROCKS OF THE ROCHESTER DISTRICT. 

The Rochester district lies in an area mapped by the Fortieth 
Parallel Survey as occupied by the Koipato formation. As has been 
already stated, later work has shown that this formation is a volcanic 
complex consisting chiefly of rhyolitic rocks, but within the district 
it contains also limestone, shale, quartzite, and some greenstones of 
igneous origin. 

The rocks having the largest areal extent near Rochester and 
those most closely associated with the ore deposits are light colored 
and are chiefly rhyolite or rhyolitic, but with them are included also 
some quartz latite, dacite, andesite, and altered quartz porphyry. 
As shown on the accompanying map (PI. VIII), these rocks occupy 
almost the whole of the eastern part of the Rochester district and ex¬ 
tend westward to Lincoln Hill. 

The formation consists of superimposed flows of rhyolite and rhyo¬ 
litic lavas, with intercalated beds of tuff, breccia, and obsidian. In 
places, as at the head of Rochester Canyon, the rocks appear to be 
agglomeratic. The rhyolites are locally very variable in texture, 
changing abruptly from dense felsitic lavas to coarse porphyries. 
Flows in Nenzel Hill and on the Sunflower ground, farther south, 
show some flow banding or lamination. 

In Nenzel Hill and on the divide a mile and a half to the north, at 
the head of Limerick Canyon, the rocks dip about 30° E. and are 
transversely sliced by a very pronounced sheeting, the dominant 
structure of the region, which dips about 60° W. The rocks are cut 
into sheets or slices from a few inches to 5 feet or more in thickness. 
This sheeting is locally accompanied by more or less profound par¬ 
allel shearing and by the development of schistosity, which is best 
seen on the weathered edges of the sheets. Slickensiding and groov¬ 
ing are also very common. Locally, at least, as shown in the Causten 
tunnel, there is another pronounced sheeting with a dip to the north 
and a less conspicuous one to the east-southeast. The rocks and the 


1 Louderback, G. D., op. cit., pp. 316-322. 



U. S. GEOLOGICAL SURVEY 
GEORGE OTIS SMITH, DIRECTOR 


BULLETIN 580 PLATE VIII 



LEGEND 


Quaternary gravels and alluvium 



Chiefly dark limestone 


\7 ' / / 

/Xv " 
v / y / / 

/- Y / . 


Chiefly gray to bjuish dark 
arenaceous fossiliferous 
limestones and shales 


\ /_\ \ 


/ 


/ \ 


\ / \ 


Acidic volcanic complex 
chiefly of rhyolite and 
rhyolitic rocks 


i i-1-r 

+ + tt 

- + + + + 

+ + + +- 
- + +• + + 

-1-1_ L 


Greenstone, altered and schistose 
volcanic rocks, chiefly basic 


-j i, h h V/i 

~i r -i r- -a -/ 
A 


Undifferentiated; chiefly light- 
colored rhyolitic rocks 
reported 




Mine 


Prospect 


JO 


Triangulation and 
topographic station 


Base and most of the claim boundaries 
surveyed by R. D. Pickett 

Geology by F. C. Schrader 


GEOLOGIC MAP OF THE ROCHESTER DISTRICT, NEVADA 

S cale 24/100 

0 1,000 2,000 3,000 4,000 5,000 6,000 Feet 


ENORAVEOAND PRINTED BY THE 11 S-SEOLOGICAL SURVEY 


Contour interval 100 feet 
1914 


1 Mile 


Koipato formation Star Peak 

formation 


















































































































































































































































































































































































ROCHESTER MINING DISTRICT, NEW 335 

ore zone are also cut by a nearly vertical east-west cross jointing into 
slices from 1 foot to 4 feet in width. 

Xenzel Hill appears to be composed almost wholly of the rhyolitic 
complex. The rocks there are considerably faulted. Besides the 
sheeting in the north end of the hill the rocks, locally at least, are 
traversed by a system of close fracture planes or joints that strike 
N. 30° W. and another system that strikes approximately at right 
angles to this structure. 

In Packard Bidge, 2 miles south of Xenzel Hill, as shown in 
figure 90, the rhyolitic rocks dip 50° WXW., apparently conform¬ 
ably beneath some rather thin bedded and less disturbed arenaceous 
limestones and shales. 



? . . , ■ 5 Q 0 _ 'poo feet 

1 • 

Figure 90.—Diagrammatic cross section of Packard Ridge, Rochester district, Nev., show¬ 
ing position of the principal ore deposits. Looking N. 30° E. C, Craggy croppings of 
silicified schistose rhyolite; O, present main ore body, 30 feet wide and 1,200 feet long; 
F-F', fault fissure ; BCTO, probable course of ore-depositing solutions. 

Similarly at the west base of Lincoln Hill, 3 miles west of Xenzel 
Hill, the rhyolites appear to pass conformably beneath the same 
limestone-shale series as at Packard, which here dips 20°-60° WSW. 
In the Packard and Lincoln Hill exposures, however, the layering in 
the rhyolites is obscure and has been less definitely determined than 
in Xenzel Hill. 

At Packard the sedimentary beds are unaltered and appear to 
have been deposited on the rhyolite. At Lincoln Hill, however, 
the limestones, which are leaden to dark bluish gray and are rather 
thick bedded, are in part metamorphosed. They are partly schistose, 
are silicified, and contain diopside, actinolite, garnet, and other 
contact-metamorphic minerals, developed near the rhyolite, which 
indicates that the rhyolite may be intrusive and later than the lime¬ 
stones, but the actual contact of the two formations is not sufficiently 
well exposed to prove that the metamorphic phenomena were caused 
by the rhyolite. 





336 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

In this connection it may be noted that rhyolite dikes, to which 
attention was called by Reid, 1 also intrude the schists and other rocks 
about a mile north of Spring Valley Pass, and the lower part of 
Limerick Canyon, according to Ransome, 2 lies in granite porphyry 
which has the appearance of being intrusive. 

A little farther from the Lincoln Hill contact the limestone beds 
are rich in poorly preserved fossil remains, some of which G. H. 
Girty has provisionally determined as crinoid stems and remains of 
ammonites, probably of Triassic age. 

The sedimentary rocks here described extend up Weaver Canyon 
and the gulch bounding Packard Ridge on the west, but their bound¬ 
ary in these localities has not been traced. 

Exposures adequate for the determination of the thickness of the 
rhyolite series do not occur in the district. From the top of Nenzel 
Hill, however, to a point below the Causten tunnel the rocks have 
a thickness of at least 500 feet. From outcrops extending inter¬ 
ruptedly farther down the slope in the head of Rochester Canyon it 
is very probable that the thickness may exceed 1,000 feet. Simi¬ 
larly, from exposures extending across the district (PI. VIII) to 
the east base of Lincoln Hill and the ridge to the south, the thickness 
is estimated at about 2,000 feet. This estimate, however, makes no 
allowance for a possible duplication of layers by faulting or for 
changes in structure, such as may occur in a region so highly 
disturbed. 

The more glassy and tuffaceous varieties of the rhyolite rocks 
occur in the upper part of Nenzel Hill, in thin layers, some of 
which resemble beds of dense quartzite. Here a dark gray speckled, 
medium-grained facies, locally called granite on Crown Point claim 
No. 1, in the northeast slope of the hill, is really a tuff or flow 
breccia and contains considerable pumiceous glass and fine dust¬ 
like volcanic detritus. 

The rocks, particularly in the mineralized areas as at Nenzel Hill, 
are in general silicified, devitrified, and sericitizech To silicification 
Nenzel and Lincoln hills and Packard Ridge owe the preservation 
of their forms, which rise above the surrounding surface. 

As stated by Jones, 3 however, the rocks retain enough of their 
original character to be recognizable in the field and in places they 
show relatively well preserved phenocrysts of quartz. 

Under the microscope the rhyolites are found to consist essentially 
of a microcrystalline to glassy groundmass in which are a few 
phenocrysts of quartz and orthoclase, with well-developed micro- 
perthite and microcline, in some varieties, and rarely a few small 
foils of altered pale-brown biotite or of green chlorite derived from 

1 Reid, J. T., oral communication. 

2 Ransome, P. L., op. cit., p. 36. 

3 Jones, J. C., op. cit., p. 738. 





ROCHESTER MINING DISTRICT, NEV. 


337 


the biotite. The rocks generally show approximate parallelism in 
the arrangement of their constituents, which in some places is clearly 
fluxion banding but in others is obscure and may have been effected 
by pressure. The latter view is supported by wavy extinction, which 
is common in the quartz phenocrysts. Spherulitic structure is com¬ 
mon in the specimens from Packard. 

The hydrothermal alteration of the rocks increases with nearness 
to the veins and ore deposits. In some places, both groundmass and 
phenocrysts, notably the feldspar, are completely replaced, or nearly 
so, by secondary silica, which, as seen in thin section, forms veinlets, 
stringers, and irregular crystalline patches throughout the slide, en¬ 
circles the quartz phenocrysts as aureoles, and lines druses. 

Apparently almost contemporaneously with the process of silicifi- 
cation there was developed in some rhyolites considerable secondary 
orthoclase, and, in some facies, microperthite and microcline. 

Sericitization is also general and has proceeded to advanced 
stages. Some orthoclase phenocrysts are almost wholly replaced by 
sericite and kaolin. A thin section from the Colligan tunnel is 
threaded by veinlets and seams of sericite, and one of a glassy por- 
phyritic rock from Packard, besides containing patches of this 
mineral, shows a network of irregular veinlets and seams of it. 

In the more mineralized areas, the rocks commonly contain finely 
disseminated pyrite, which weathers to limonite and hematite and 
tints the rocks light rusty brown. 

Similar rocks occurring in Cottonwood Canyon, 7 miles to the 
north, were analyzed for the Fortieth Parallel Survey, 1 and Jones 2 
regards one of the analyses (B, in the subjoined table) as indicating 
the general composition of the rocks in this area. 

Analyses of rhyolites from the Humboldt Range. 



A. 

B. 

C. 


76.80 

11.64 

1.10 

Trace 

.43 

2.53 

6.69 

.77 

74.74 

14.14 

.79 

.39 

1.51 

.92 

5.29 

87.00 

9.6 

1.2 

Trace. 













.2 


Trace. 



1.88 





99.96 

99.66 

98.00 


A. Typical rhyolite from the Mopung Hills, forming the southern end of the Humboldt 
Range. Inserted for purposes of comparison. M. It. Woodward, analyst. U. S. Geol. 
Expf. 40th Par., vol. 2, p. 736, 1877. 

It A brownish-gray rock containing both feldspar and quartz, from Cottonwood Canyon. 
B. E. Brewster, analyst. U. S. Geol. Expl. 40th Par., vol. 2, p. 722, 1877. 

C Partial analysis of a specimen trom the silicihed hanging wall, a few feet from the 
ore body in Codd lease in Nenzel Hill. W. S. Palmer, analyist, Mackay School of Mines, 
Reno, Nev. Min. and Sci. Press, vol. 106, p. 738, 1913. 


1 Hague, Arnold, and Emmons, S. F., op. cit., p. 722. 

58849°—14-2 


2 Jones, J. C., loc. cit. 











































338 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

Analysis C is regarded by Jones as illustrating the increase in 
silica near the ore bodies, some of which, as he states, consist almost 
wholly of quartz that has replaced the rhyolite. 

Analyses B and C agree well in their more important constituents 
with that of the typical rhyolite, A, except that C, as was to be 
expected, is high in silica and B is low in sodium, which from the 
alteration that has taken place in the rock is not surprising. 

The areas shown on the map as greenstone, one three-fourths of 
a mile northeast of Lincoln Hill and the other at Spring Valley 
Pass, contain chiefly highly altered, compressed, and partly schistose 
dark rocks, which appear to be chiefly metamorphosed andesite por¬ 
phyry, or possibly in some places diorite porphyry, with some basalt 
or diabase. There is also some light-greenish sericitic and micaceous 
quartz schist. The darker diabasic rocks contain some finely dis¬ 
seminated pyrite, mainly in or associated with the altered augite 
phenocrysts as shown in specimens from Sacramento Canyon and 
Spring Valley Pass. 

In the schist in the west slope of Lincoln Hill, wdiich he calls 
mica-tourmaline schist, the tourmaline, according to Jones, 1 is a 
pink variety or rubellite, containing, however, the predominating 
alkali soda rather than the usual lithium, and mica that is asso¬ 
ciated with it also appears to be the soda mica, paragonite. 

The andesitic rocks, in which the ferromagnesian minerals are 
highly altered, contain residual phenocrysts of calcic plagioclase 
and are traversed by veinlets of secondary quartz and calcite. The 
diabase, in part at least, is less altered dynamically than the other 
rocks and probably represents later intrusive sheets and dikes. 

ORE DEPOSITS. 

LODES. 

GENERAL FEATURES. 

The deposits of the Star Peak Range in general are silver-gold 
ores, characterized mineralogically by the presence of one or more 
of the sulphantimonites. They occur chiefly in the Star Peak forma¬ 
tion in structurally favorable places, and although rich near the sur¬ 
face have not proved persistent to great depth. To these statements 
the Rochester ore deposits, geologically and in part mineralogically, 
form an exception. They are chiefly antimonial silver and gold bear¬ 
ing deposits but they occur mainly as replacement deposits in the 
sheeted rhyolite and are irregular, lodelike, or veinlike in form. 
Their material is chiefly quartz. The associated minerals observed 
are given in the table on pages 340-341. 


1 Jones, J. C., loc. cit. 





ROCHESTER MINING DISTRICT, NEV. 


339 


The deposits occur in two north-south belts, each about a mile in 
width—the Nenzel Hill belt on the east and the Lincoln Hill belt 
on the west. The belts parallel the range and approximately the 
dominant structure of the country rock, to which the deposits in 
large measure conform. 



% 




Minerals of the Rochester district and vicinity, Nev. 


340 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 


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342 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 


NENZEL HILL BELT. 

The Nenzel Hill belt of deposits, which is by far the most impor¬ 
tant, extends from Packard northward to Spring Valley Pass, its 
length being nearly 5 miles. Nenzel Hill, which contains the most 
valuable part of the deposits, is situated near its middle point. 

NENZEL HILL ORE DEPOSITS. 

The ore deposits of Nenzel Hill occur as replacement veins and 
allied deposits, in part composed of small veins and stringers of 
quartz, but chiefly altered, silicified, and replaced rhyolite. The ores 
contain chiefly silver, but carry also gold, which in some of the ore 
amounts to 60 per cent of the value. 

The croppings are locally prominent, generally iron stained, and 
commonly constitute rich shipping ore. 

The quartz is locally porous, cellular, and drusy. The vugs are 
small, generally parallel, lenslike in outline, and are lined with fine 
comby quartz, whose crystals may nearly coalesce, leaving only a 
narrow, irregular watercourse along the median plane. Some of the 
quartz is brecciated, crushed, or laminated, and in places ore min¬ 
erals have been deposited in the fractures. Some faulting along the 
veins is shown by the local occurrence of 6 or 8 inches of gouge on 
the footwall. 

The trend and general relations of the more important veins and 
lodes are shown in figure 91. They vary from a few feet to 40 feet 
or more in width and range from 100 to 3,700 feet in length. Col¬ 
lectively they extend for nearly a mile. The known deposits are 
mostly on ground owned by the Rochester Mines Co. and the Roches¬ 
ter-Weaver Mining Co. They comprise 12 claims and are commonly 
known as the Nenzel group. 

The deposits occur along fissures and shear zones and locally 
within fissures. They follow approximately two of the sheeting or 
joint systems described under the heading “ Geology ” (p. 334). One 
set trends approximately north, and the other N. 30° E. The latter, 
as indicated by development to date, is much the stronger and more 
important system, and is apparently also the younger. Its veins 
have a horizontal length of nearly 4,000 feet, and some of them have 
a known vertical range of 500 feet or more. In places they join or 
intersect veins of the northward-trending system. Both systems 
dip steeply to the west at angles of 60° or more. A few short and 
relatively unimportant veins occur on the east-west sheeting. 




ROCHESTER MINING DISTRICT, NEV. 


343 


MINING DEVELOPMENT. 

The deposits are opened mainly on the Rochester Mines Co.’s 
ground, where more than 7,000 feet of work has been done, mainly 
on the west or main Nenzel Hill vein, which belongs to the north¬ 
east-southwest system 
and has a length of 
nearly 3,000 feet. On 
the Crown Point No. 

1 claim, workings on 
the Codd and the Big 
Four or Platt leases, 
shown in Plate YITI 
(p. 334) and figure 
89 (p. 329), have at¬ 
tained a depth of 300 
feet or more, and 
levels have been run 
at intervals of 50 feet. 

Here at the time of 
visit the ore zone, as 
exposed to the depth 
of about 100 feet, had 
a width of 32 feet. It 
showed two veins of 
ore, each 6 to 8 feet 
wide, averaging $30 to 
the ton. The ore then 
exposed in some por¬ 
tions of these veins 
averaged several hundred dollars to the ton, and some was even 
richer. The entire zone, as then exposed, was said to average $12 to 
the ton. The two veins were composed of numerous irregularly dip¬ 
ping stringers of ore-bearing quartz, separated by silicified rhyolite, 
which in many places was also ore. The quartz and vein material in 
general was crushed and a considerable portion of it was moderately 
well banded. 

On December 1, 1913, the general conditions just described were 
authentically reported to continue to the bottoms of the mines, with 
no indication of diminution in the quantity or quality of the ore. 
The workings have been in good ore from the surface down. In the 
lower part of the Big Four mine the lessees at the end of the year 
1913 had opened up a block of ground 110 feet deep by 80 feet long. 
At the same date the Codd lease, developed by about 2,500 feet of 



Figure 91. —Plan of the principal lodes and veins in 
Nenzel Hill, Rochester district, Nev. 










344 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

work and credited with a production of over 9,000 tons of ore, had 
an ore shoot known to be 150 feet deep and 160 feet long. 

In March the operators of the Big Four mine reported 3,000 tons 
of ore in the stopes ready for shipment. Late in April they were 
stoping a width of 7 feet of good shipping ore just beneath the 50- 
foot level stope, which last autumn produced $100,000, and on the 
160-foot level south and on the lower levels stoping, raising, and 
sinking showed that the ore body in places has a width of 14 feet. 

In the Codd mine, late in January, 1914, an ore shoot was opened 
on the hanging-wall side of the 150-foot level. This averaged about 
$65 to the ton, of which about $6 was in gold. This mine, from the 
surface down to the bottom level, still contains large bodies, 4 to 14 
feet wide, of milling ore, amounting to about 25,000 tons and averag¬ 
ing about $14 to the ton. 

Late in April, 1914, the shaft on the Codd lease had attained a 
depth of 500 feet, and good ore was being mined from the 320-foot 
level north, and in May the main vein, with good ore in the east 
crosscut on this level, was struck. The workings were being con¬ 
nected with the main Causten level, which is 400 feet below the out¬ 
crop of the vein. 

According to later reports, on the 425-foot level a width of 10 feet 
of the vein averages $20 and 3 feet of it about $35 to the ton, and 
much $25 ore is said to be blocked out. Here also a 40-foot crosscut 
to the east from the bottom of the shaft has encountered a new vein, 
thought to be the “ back ” vein, which is 12 feet in width and in ore 
content compares favorably with the main vein. Four feet of it 
averages about $28 to the ton and the rest is good milling ore. The 
location is on the Causten lower tunnel level, at 800 feet from the 
portal, and the vein is thought to contain much workable ore below 
this level and the surface. 

Developments in September, 1914, have shown the presence of this 
vein, with practically the same width and ore tenor as above de¬ 
scribed, extending through the deep parts of the Big Four and Four J 
mines, thus indicating a continuous length of 1,000 feet of milling ore 
on the several leases at depths of 400 to 600 feet. 

The Causten or Four J lease, about 1,000 feet north of the Codd 
lease, is opened mainly by a lower tunnel, the Causten or main cross¬ 
cut tunnel, which is 300 feet lower than the collar of the Codd shaft, 
and by an upper tunnel 300 feet above the lower one. At the time of 
visit the upper tunnel, 265 feet in length, connected with 120 feet of 
drift and had yielded some $6 ore. 

The lower tunnel at that time had a length of nearly 200 feet. It 
penetrated altered decomposed brownish iron-stained blocky rhyo¬ 
lite, less siliceous than the average rock in Nenzel Hill. Some of 


ROCHESTER MINING DISTRICT, NEV. 


345 


the less oxidized rock near the face contains pyrite finely dissemi¬ 
nated. The tunnel driven to the east follows a zone of crushed, 
altered, and silicified rhyolite and rhyolite breccia 18 inches wide 
which in places gave assays of more than $300 to the ton, but, as in 
the upper tunnel, the average material is not of shipping grade. 
Several tons of it lay sacked on the dump. In some of this ore 10 
per cent of the value is said to be in gold. The country rock is cut by 
joints into cuboidal blocks 2 to 3 feet across. 

By December 1, 1913, the tunnel had been extended to a length of 
a thousand feet, giving a depth of about 400 feet on the main vein, 
and a body of $16 ore had been cut. In January, after further 
sinking in the bottom of the Codd mine and drifting in the Causten 
ground, a new ore shoot 3 to 4 feet wide was reported. The ore in 
this shoot is said to resemble that of the Colligan lease on the Weaver 
ground, on the southern slope of Nenzel Hill, and to average about 
$100 to the ton, with two-tliirds of its value in gold. This ore 
body, it may be observed, is apparently at the same elevation as the 
ore of the Colligan workings and is probably at about the same 
geologic horizon. 

Decently it has been reported that workings from this tunnel have 
been extended to the depth of 520 feet, the greatest yet attained in 
the district, and that the vein, which continues about 8 feet in width 
to this depth, consists chiefly of milling ore, of which by June the 
mine had blocked out and accumulated 20,000 tons. There are, how¬ 
ever, some bodies of richer ore from which the Four J lessees began 
shipping early in March. Subsequently, in an upraise from the main 
level, a shoot of $30 ore 2-J feet wide was encountered, which is 
thought to be a continuation of the shoot exposed in the north end 
of the Codd lease. 

The operators of the No. 4 lease, which lies between the Codd and 
the Causten leases, ship from time to time a carload of $30 ore from 
relatively shallow workings. About a thousand feet north of these, 
the lessees of Block 8, on the Crown Point No. 3 claim, opened by 
shaft and tunnel in the northeast slope of Nenzel Hill at 7,000 feet 
elevation, are also working in good ore. The Camille Rock lessees, 
also on the Crown Point Mining Co.’s ground, near by, are reported 
(April, 1914) to be working a 6-foot vein of ore, mostly of shipping 
grade, which has been stripped on the surface and shows well for a 
distance of 400 feet. At the depth of 65 feet the vein contains a body 
of old-silver ore 6 feet in width, which assays from $40 to $80 to 

to 

the ton. 

The ore minerals in the deposits of Nenzel Hill occur chiefly in 
quartz that has replaced rhyolite and are sporadically distributed 






346 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

through this in small aggregates, much of the ore having a blotchy 
or mottled appearance. To some extent they occur in the vugs, and 
secondarily they follow lamination or fractures in the quartz. 

The silver-bearing minerals, which are the important constituent 
of the ores, owing to their fine-grained aggregation, are not easily 
determined. In much of the ore bindheimite, a yellowish-green min¬ 
eral consisting chiefly of hydrous lead antimonate and resulting from 
the decomposition of other antimonial ores, is common. From this 
occurrence it appears that silver-bearing sulphantimonites may be 
present. Among the minerals Jones 1 has recognized pyrargyrite. 
Argentite, which is regarded by Mr. E. B. Mills, superintendent of the 
Rochester Mining Co., as probably the principal ore mineral, seems 
to be present generally, accompanied in places by a little proustite. 
Scales of native silver are visible here and there, and rarely, with 
the pocket lens, a few specks of free native gold may be seen. The 
Big Four and Codd ore averages one four-hundredth of an ounce, or 
about 5^ cents in gold to the ton, but the gold is said to increase with 
depth. Other silver minerals reported by mining men are cerargyrite 
and bromyrite. At the time of the writer’s visit the ore minerals 
could be more satisfactorily studied in material from the No. 4 shaft 
on the Crown Point No. 1 and in neighboring small openings in the 
northeast slope of Nenzel Hill than in that from the larger workings. 

The ore, according to smelter returns, contains about 93 per cent 
silica. Besides quartz and the minerals just mentioned it contains 
some pyrite, a little chalcopyrite, and in places a very little spha¬ 
lerite and galena. The ore is commonly stained pale brown by oxi¬ 
dation products, particularly by limonite and hematite derived from 
the pyrite. In places it is stained green or bluish by malachite and 
azurite derived from the chalcopyrite. In some places these copper 
carbonates line vugs and appear to be of recent deposition. 

In the southern part of the Nenzel Hill area, on the south slope 
of Nenzel Hill, the Rochester-Weaver Mining Co.’s ground has been 
opened by about 4,000 feet of work, including a 430-foot adit. The 
principal openings are on the Colligan and Shea lease blocks. The 
ore bodies have been found to extend to the depth of 350 feet. At 
that depth three veins have been crosscut. 

At the Colligan lease, worked by the Rochester Nugget Mines Co., 
the country rock is a purplish-brown porphyritic rhyolite, consider¬ 
ably altered and traversed by veinlets of sericite. The strike of the 
vein, N. 17° E., is intermediate between that of the northward trend¬ 
ing system and that of the north-northeastward trending system. It 
is probably a continuation of the West vein, although its connection 
with that vein has not been established. It is in general nearly 


1 Jones, J. C., loc. cit. 



ROCHESTER MINING DISTRICT, NEV. 347 

vertical, dipping here to the west and there to the east. It ranges 
from 1 foot to 3J feet in width. 

The vein is composed of brownish or yellowish fine-grained quartz 
and silicified rhyolite, the color being due to limonite. Most of the 
ore is soft and pulverulent, but the vein contains also some harder 
ore, like that of the Codd and Platt mines. At the time of the 
writer’s visit the workings comprised a 55-foot crosscut tunnel, 90 
feet of drift, and a 16-foot winze. The mine had produced 90 tons 
of $27 ore, of which 40 per cent of the value was in gold and the 
remainder in silver. According to returns of the Mason Valley 
Mines Co.’s smelter, the ore contains also 13 per cent of iron. 

By December, 1913, the Colligan mine had attained a depth of 
210 feet and the lessees had shipped 320 tons of ore, which averaged 
nearly $42 to the ton. More than one-third of the value of this ore 
w T as in gold. In May much of the ore was reported to average $75 
to the ton. 

On the neighboring Gillespie or Shea-Kelleher lease, about 1,000 
feet east of the Colligan, is an incline shaft, 600 feet deep, on what 
appears to be a 16-foot lode, which is parallel to that of the Colligan. 
The workings are on the southwest slope of Nenzel Hill, in brown 
rhyolite. Later reports indicate that the mine contains an ore 
shoot 4J feet wide, which averages about $50 to the ton in gold and 
silver. Prior to December 1 the mine had produced over 170 tons 
of ore, which averaged approximately $26 to the ton. At the time 
of the writer’s visit about 6 tons of good-looking quartz ore lay on 
the dump. The ore contains some pyrite. In August the mine was 
reported to have blocked out over 10,000 tons of ore ready for 
stoping. 

Operators of neighboring leases, the Cole, Friedman, and Case, 
also on the Weaver ground, on the south slope of the hill, have made 
small shipments. Late in March, 1914, it was reported that a shoot 
of $100 ore, 18 inches wide, in which the value is chiefly in gold, was 
struck on the Cole lease, at a depth of 125 feet. A carload shipped 
in May is said to have yielded returns of $142 to the ton in gold. 

The East vein or ledge outcrops along the upper east slope of 
Nenzel Hill, lying approximately parallel with the West vein, from 
which it is 1,200 to 1,400 feet distant. It has a known length of 
about 1,000 feet, mainly wuthin the January Fraction claim, but it 
extends for a few hundred feet into the Crown Point No. 1 claim, 
to the north. The lode shows rugged croppings of silicified rhyolite, 
which dip 75° W. into the hill and toward the east form a steep 
scarp about 100 feet high. 

The lode is opened at several places. The most important opening 
is at the north end, in the Roy Ridge mine. At this place 8 tons of 
ore, said to average $100 in silver and $1.50 in gold to the ton, was 



348 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

taken from a 50-foot shaft. The lode is from 3 to 5 feet wide. Both 
the vein and the wall rock contain disseminated pyrite and a very 
little pyrrhotite. 

The Nenzel Hill ore deposits, if they persist downward, as ap¬ 
pears probable, are admirably situated for working through crosscut 
tunnels, which, driven from the east or west side of the hill, would 
give from 600 to 1,000 feet of depth, according to the location of the 
tunnel. 

In the adjacent part of Sunflower Bidge, which incloses Bochester 
Canyon on the south, and in the saddle separating this ridge from 
the south end of Nenzel Hill, several veins have been opened on the 
Sunflower group of claims, owned by the Bochester Belmont Mines 
Co. Here the Sunflower vein, opened at the time of visit by a 50-foot 
shaft south of the saddle, has a width of 10 feet and dips steeply to 
the east in rhyolite. At present (May, 1914) a lease being operated 
in the saddle is said to be producing good ore, and from one of the 
openings pockets of very rich surface ore, averaging 27 ounces in 
gold and 362 ounces in silver to the ton, are reported to have been 
taken. 

The Hockley-Boughton lease, almost adjoining the Sunflower prop¬ 
erty on the west, is also said to be shipping good ore, a carload of 
which averaged $87 to the ton. 

The Limerick gold mine is opposite the Sunflower on the upper south 
slope of the ridge that bounds Bochester Canyon on the north. It is 
located on patented ground, which extends across the ridge and lies 
in part on the Limerick Canyon side. It is owned by C. N. Miller, of 
Fairport, Cal. The country rock is rhyolite, which is stained with 
limonite and locally has a honeycombed structure. In general the 
rock is so crushed, sericitized, and otherwise altered that there is 
scarcely anything for the prospector to follow. A sheeted structure 
dips 25° W., and silicified croppings one-eighth of a mile up the slope 
dip 60° W. 

The mine is opened mainly by a 90-foot incline of 15°, which ex¬ 
tends N. 20° W. along two or more ore-bearing layers of breccia 
composed of quartz and rhyolite. The layers in general dip west, 
but are very irregular. The gold is sporadically distributed in very 
fine particles. Cerargyrite is sparingly present, and proustite is re¬ 
ported. At the time of the writer’s visit a small consignment of 
$125 ore had been shipped, and about 5 tons were sacked on the 
dump. 

A moderate amount of sinking and systematic east-west cross¬ 
cutting at right angles to the well-known dominant structure and 
vein systems of the district would be likely to show whether the prop¬ 
erty contains any well-developed ledge or extensive workable de¬ 
posits. 


ROCHESTER MINING DISTRICT, NEV. 


349 


The Plain view mine is nearly a mile north of the Limerick and a 
half mile south of Panama, in the open head of Limerick Canyon, 
at about 6,300 feet above sea level. It lies in altered, silicified, and 
very highly sericitized gray rhyolite and is opened by considerable 
work extending for some distance below and above the ore road of 
the Rochester mines. 

The lower tunnel, 500 feet long, runs N. 55° E. on an irregular 
shear zone or fault plane, which dips 60° NW. The rock is crushed 
and partly silicified, iron-stained rhyolite, considerable portions of 
which for a few feet in width are said to average about $9 to the 
ton, chiefly in gold, some of which is visible in the rock. The de¬ 
posits, however, are apparently too low in grade to be workable under 
present conditions. 

About half a mile northeast of the Plainview mine, on the west 
side of the pass between Limerick and American canyons and at 
about 6,400 feet above sea level, are strong croppings on what is 
known as the Orms prospect. These croppings show altered rhyolite, 
or perhaps dacite, for besides much quartz the rock contains con¬ 
siderable lime-soda feldspar, and some chlorite after biotite. 

The ledge, from 3 to 8 feet in width, strikes approximately east 
and west and is opened mainly by a 100-foot tunnel drift. It is 
composed of silicified rock, closely banded by veins and stringers of 
quartz, and shows considerable free gold, but the ledge at the time 
of the writer’s visit appeared to be irregular and difficult to follow. 

Just over the ridge from the Orms prospect, on the southeast slope 
of the pass between Limerick and American canyons, are some de¬ 
posits that differ from those of the Nenzel Hill class in that they 
are more distinctly of vein character, without the replacement fea¬ 
tures which are so characteristic in Nenzel Hill. The country rock 
is rhyolite or quartz latite porphyry, resembling that at the Orms 
prospect. It occurs in heavy sheets or flows, dipping 50° E. A por¬ 
tion of the rock which crops in a rather prominent reef several feet 
in width appears to be a later intrusive sheet or dike. 

The deposits consist of a series of approximately parallel quartz 
stringers and veins, which also dip 50° E. in approximate conformity 
with the porphyry. They range from a few inches to 2J feet in 
width. From croppings and prospects in the northeast slope of the 
hill it is estimated that one or more of the veins has a vertical range 
of at least 200 feet. The metallic minerals conspicuous in the veins 
and stringers are sphalerite, galena, and pyrite, all more or less in¬ 
termingled. They occur crudely banded or as streaks and are not 
present in workable quantity. The metal for which the deposits are 
being exploited is said to be silver, the silver-bearing minerals being 
apparently associated with the galena and only sparingly present. 


350 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

SOURCE OF THE NENZEL HILL ORE DEPOSITS. 

The Nenzel Hill ore deposits, as shown by the quartz phenocrysts 
which they contain, and by their outward transition from nearly 
pure quartz into rhyolite, were formed by replacement of that rock, 
already rich in silica. Although the contact between the veins or 
ore zones and the wall rock is in general well defined, its undulatory, 
irregular character is also indicative of replacement. 

The deposits have supposedly been formed by ascending hydro- 
thermal solutions derived from some intrusive magma. This magma 
may have been that corresponding to one of the volcanic rocks or 
that of some underlying granite, possibly a southerly extension of 
the granite mass of Rocky Canyon. 

The heated solutions probably continued to ascend long after the 
intrusion of the magma. The water of Black Knob Spring, near 
Packard, is slightly warm, and in American Canyon the rocks in a 
200-foot shaft are reported to be above the usual temperature for 
rock at that depth. But the heat in these places is likely to be due 
to later processes than those connected with the origin of the ore 
deposits. 

In a few places on the south slope of Nenzel Hill structures were 
observed that suggested the pseudomorphic replacement of calcite 
by silica, but the evidence was too indefinite to justify the conclusion 
that silica has extensively replaced a calcite gangue as it has in 
some districts in Nevada and Arizona. 

The irregularity in the lateral extent of silicification, considered in 
connection with the greater abundance of primary quartz pheno¬ 
crysts in the less silicified portions of the deposits as compared with 
the more silicified, indicates, as urged by Whyttock, 1 that silicifica¬ 
tion and ore deposition were most active in the more feldspathic 
portions of the rocks, the feldspar being particularly susceptible 
to metasomatic replacement. 

PACKARD ORE DEPOSITS. 

The Packard ore deposits resemble in some respects the Nenzel 
Hill deposits, but differ markedly from them in being less well de¬ 
fined and less silicified. They occur in Packard Ridge, a broad, 
gently sloping spur at the south end of the Nenzel Hill belt, at an 
elevation of about 5,850 feet. A cross section of the hill is shown in 
figure 91 (p. 343). 

At the time of the writer’s visit the ground had been opened in 
four contiguous claims, known as the Packard group (PI. VIII). 
The first location here was made in December, 1912, by Henry Lund. 

1 Whyttock, P. R., oral communication on the ground; see also Min. Rev., vol. 15, 
No. 2, p. 21, Apr. 30, 1913. 




ROCHESTER MINING DISTRICT, NEY. 


351 


The rich silver ore now being worked was found by R. Ray in the 
following May, and soon thereafter the property was sold for $5,000 
to the Rochester-Packard Mines Co., which at once began operations, 
and late in May was shipping ore. 

Along the crest of the ridge a belt of craggy silicified rhyolite, 100 
feet wide, commonly known as the “ dike,” indicated by C in figure 
91, rises about 12 feet above the surface. The croppings are sheeted 
like the adjoining rhyolite, of which they appear to be only a silici¬ 
fied part. They are also traversed longitudinally by some vertical, 
slickensided surfaces, and the “ dike ” apparently is a silicified fault 
zone. 

In a few places, where the rock has not been rendered schistose, it 
appears fresh and resembles Tertiary rhyolite, but under the micro¬ 
scope it is found to be devitrified, silicified, and sericitized. 

The ore deposits, as shown in figure 90 (p. 335), occur on both 
sides of the fault zone and are generally parallel to it in strike 
though not in dip. They conform to the general layering and 
schistosity of the rhyolite, the ore bodies on the southeast side of the 
fault zone dipping toward that feature, whereas those on the north¬ 
west side dip away from it. Very little ore occurs in the fault zone 
itself. 

The croppings of the ore deposits, unlike those of the fault zone, 
are not prominent and in some places are slightly lower than the 
general surface. They consist mainly of mineralized schistose 
rhyolite, which generally constitutes shipping ore from the surface 
down. The widespread occurrence of ore at the surface has led 
many to believe that the deposits as a whole represent a great blanket 
vein. 

The best exposure of the deposits at the time of the writer’s visit 
was on the Packard No. 2 claim and on the Packard Fraction adjoin¬ 
ing it on the west. At this locality, 150 feet west of the silicified 
fault zone, the deposits occupy the greater part of a belt about 30 feet 
wide, whose known length is about 1,200 feet. This zone is marked 
“ O ” in figure 90 (p. 335). 

In places the ore had been stripped by plow and scraper and was 
being worked in several openings from 1 to 8 feet in depth. From 
one of the main pits, about 10 feet in diameter by 8 feet in depth, 
a carload of ore had been shipped which averaged $61 to the ton— 
about $58 in silver and $3 in gold. 

Work was being done in 8 or 10 similar shallow openings on the 
Jackson, Cold Storage, Enterprise, and other ground on the east 
slope of the ridge, where the deposits extend interruptedly from the 
vicinity of the fault nearly to the base of the ridge. 

The ore minerals appear to be chiefly cerargyrite and argentite. 
They occur in the schistose and partly silicified and replaced rhyolite. 


352 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

Much of the ore is a schist with a silvery sheen, and its general 
appearance gives little suggestion of its value. In some varieties, 
however, purple or reddish-gray iron-stained quartz is present locally 
in bodies or lenses several or more inches in width, which, however, 
are irregular and ill defined and in part at least have been deposited 
by replacement. 

Some siliceous portions of the ore are speckled and in places honey¬ 
combed by cavities from which pyrite has weathered out and which 
are now occupied in part by hematite and limonite. In some places 
silver appears to occur in these cavities, associated with the iron. 
Small faults and sharp buckling of the rhyolites against the quartz, 
which is also shattered, show that considerable movement took place 
after the quartz was deposited. 

The Packard ore deposits unquestionably have a genetic connection 
with the fault zone. They were probably derived from siliceous 
hydrothermal magmatic solutions, which, in ascending the fault fis¬ 
sure shown at F-F' in figure 90 (p. 335), deposited the quartz and 
ore minerals by metasomatic replacement in certain layers or por¬ 
tions of the rhyolite. The rock replaced, as in Nenzel Hill, was 
probably less siliceous and more feldspathic than the present country 
rock. This selective action apparently explains why ore minerals 
are only very sparingly present in the silicifiecl fault zone itself. 

As the fissure, which is nearly vertical, cuts the inclined forma¬ 
tions obliquely, the deposits in the beds to the east or right of the 
fault, as shown in figure 90 (p. 335), were deposited by solutions 
which on leaving the main fissure ascended, whereas those to the west 
or left were deposited by solutions which on leaving the fissure de¬ 
scended, as indicated by the curved arrow at T in figure 90. When 
ore deposition took place the rocks, as indicated in the figure, ex¬ 
tended far above the present surface of the ridge, to which they have 
since been reduced by erosion. This erosion has shifted the outcrop 
of the ore zone (O in fig. 90) to a distance of 150 feet from the fault, 
from which it is now separated by a belt of barren rock. The 
deposits to the right or east of the fault may be expected in general 
to connect with the fault fissure in depth, and below any enrichment 
by oxidation that may have taken place from the surface they should 
show increase rather than diminution in tenor with depth and with 
nearness of approach to their source. With some offsets due to move¬ 
ment along the main fault zone these ore deposits east of the fault 
probably continue to depth beyond the fault (F-F' in fig. 90), but 
until the amount of throw is determined their exact positions must 
remain unknown. 

On the other hand, the deposits to the left or west of the fault, 
which are now the main source of the camp’s production, do not, if 
the explanation of their origin is correct, hold out much promise of 


ROCHESTER MINING DISTRICT, NEY. 


353 


great downward persistence. The ore now being mined here is ap¬ 
parently the result of surface enrichment in the oxidized zone and 
represents in large measure a concentration from portions of the 
deposits now eroded away. (See fig. 90.) The continuation of this 
relatively high-grade ore to great depths is not to be expected. 

It is possible that deeper ore zones that do not outcrop may occur 
between the ore zone (O) now being worked and the fault. This 
could be determined by sinking and crosscutting on the west of the 
fault, preferably from the bottom of fairly deep workings in the 
ore zone. Strong probability that the down-thrown portions of the 
ore beds east of the fault may be found here lends encouragement and 
purpose to the undertaking. 

A quartz vein 2J feet wide, on the north end of Packard No. 2 
claim, occupies a well-defined fissure in the rhyolite. The vein 
strikes N. 25° W. and dips 80° SW. It is composed of vitreous 
quartz, which carries only a little gold and practically no silver. Its 
course is nearly at right angles to the trend of the main deposits of 
the camp, with which it apparently has no connection. On the dump 
were seen a few crystals of smoky quartz an inch and a half in di¬ 
ameter, some with perfect pyramidal termination, which appear to 
have come from the vein. 

In October, 1913, the operators of the Packard property were 
reported to have opened a 3-foot vein of rich silver ore, some of it 
running as high as $400 to the ton. The exact location of this vein 
has not been learned. 

During the winter and spring press notices of development re¬ 
ported continued work on the deposits here described and the dis¬ 
covery of new ones containing bodies of both shipping and milling 

ore. 

Late in April, 1914, a new 11 to 20 foot vein, mostly of $25 ore, was 
reported to have been discovered about 200 feet down the slope to the 
west or hanging-wall side of the main ore zone. (See O in fig. 90.) 
As its dip is steeper than that of the main ore zone, to which its 
strike is also oblique, it should join or intersect that zone at no great 
depth. On the first level it is said to contain about 8 feet of good 
milling ore and 3 feet of high-grade shipping ore, which averages 
about $60 to the ton. The ore is described as composed mainly of 
stringers and druses containing much horn silver. Associated with 
slips, which are said to be common in the vein, the miners report 
considerable “ talc ” or gouge, which averages about $21.50 to the 
ton in silver. 

Late in May another vein or ore zone, 75 feet wide, is reported to 
have been discovered, from which a carload of $100 ore was shipped, 
and some specimens, each weighing several pounds, averaged 3,000 
58849°—14-3 





354 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

ounces in silver to the ton. In September it was reported that the 
lower workings, on what is probably an extension of this zone, have 
opened a body of milling ore approximately 100 feet wide, 20 feet 
thick, and 65 feet or more long, the developments in the last-named 
direction still being in ore. This body also contains a few ore shoots 
of shipping grade. One shoot 8 feet in width is said to average 
about $120 in silver and $11 in gold to the ton. 

In July and August the Kromer-Hampton lease, which is on 
Packard ground, was said to be shipping about 100 tons a month 
of ore averaging about $70 to the ton, and the Nevada-Packard Co. 
3 to 4 carloads a month of ore averaging about $65 to the ton. The 
company is said to have decided to build a mill to treat the ore by 
amalgamation and cyanidation. 

With the completion of the railroad into the district shipments of 
Packard ore will be greatly increased. Much of the ore produced in 
this area still comes from open-day workings. 

LINCOLN HILL BELT. 

GENERAL FEATURES. 

The Lincoln Hill belt, as shown by the distribution of the claims 
in the western part of the area (PL VIII), extends from Weaver 
Canyon northward across Rochester and Limerick canyons and 
apparently also across the crest of the range into Spring Valley, 
on the north. 

Here the newly described deposits, which early in 1913 attracted 
much attention and determined the location of Lower Town, occur 
mainly in Lincoln Hill, where at the time of the writer’s visit there 
were several producing properties from which shipments of high- 
grade ore had been made, and where some very rich ore continues 
to be found from time to time. 

LINCOLN HILL DEPOSITS. 

Lincoln Hill is an elongated oval mass about a mile long and 
three-fourths of a mile wide, rising to an elevation above sea level 
of 6,600 feet, or about 1,200 feet above Rochester Canyon, which 
adjoins it on the south. It is separated on the north from Gold 
Ridge, of Oro Fino fame, by High Grade Canyon. It is composed 
chiefly of rhyolitic rocks in which the dominant structure is a pro¬ 
nounced sheeting accompanied by shearing and schistosity. These 
structures strike N. 30° W. and dip 40° WSW. A second sheeting, 
which in strike approximately parallels the hill, dips 65° NW. 

In the rhyolite are numerous quartz veins and stringers, which 
are the source of the rich float found on all sides of the hill and which 
during the boom occasioned the staking of nearly 100 claims. They 


ROCHESTER MINING DISTRICT, NEV. 


355 


comprise mainly two sets. The more important one follows approxi¬ 
mately the strike of the northeast-southwest sheeting and appar¬ 
ently corresponds to the main vein system in Nenzel Hill. The other 
set, at about right angles to the first set, strikes approximately north¬ 
west and forms an angle of about 25° with the N. 30° W. sheeting. 
To this set apparently belongs also the vein of the Oro Fino mine, 
a mile northwest of Lincoln Hill. 

The Lincoln Hill veins are smaller than the Nenzel Hill veins and 
more nearly resemble veins of the filled-fissure type. They contain 
tourmaline, specularite, and other minerals in quartz, and the valu¬ 
able metal is almost entirely gold. Bromyrite has been found by 
Mr. J. Phelps at the south base of the hill. 

The deposits occur chiefly in six or eight veins on the west slope 
of the hill. The principal openings on them are the Summit and 
Supreme mines on the northwestward-striking system and the For- 
villy mine on the northeast-southwest system. 

On the latter system, on the Abe Lincoln No. 2 claim, at an eleva¬ 
tion of 6,400 feet, the Forvilly mine, owned by Messrs. Campbell 
and Forvilly, is opened mainly by two 40-foot shafts, one on each 
of two veins which lie about 20 feet apart and dip 80° NW. Here 
the southeast vein is 3 feet in width and the northwest one is wider. 
Stoping is done on both veins to the northeast of the shafts. The 
walls are good but generally “ frozen ” and without gouge. Tiie veins 
are composed mainly of quartz, in small part replacing rhyolite, and 
of altered and silicified rhyolite. In places they are vuggy or porous. 

The ore in places is crudely branded. Its contents in gold and 
silver are approximately equal in value. With it is associated some 
finely disseminated pyrite. About 120 tons of ore, averaging about 
$58 to the ton, had been shipped at the time of the writer’s visit, and 
5 tons were sacked or piled on the dump. 

The Summit or upper Forvilly mine, about TOO feet east of the 
mine just described, is in a saddle in the crest of Lincoln Hill at an 
elevation of 6,450 feet. Its vein, which belongs to the northwest- 
southeast system, is 2J feet or more in width and dips 60° NW. It 
is opened by an incline shaft. The country rock is rhyolite. The ore, 
of which several tons were lying sacked on the dump at the time 
of the writer’s visit, is apparently of good grade and shows much 
free gold. It resembles the ore of the Supreme mine, next to be 
described, which, together with the fact that it is approximately on 
the projected course of the Supreme vein, suggests that the deposits 
at the two mines may be on the same vein. 

In September, 1914, development of the Forvilly mines is reported 
to have continued with gratifying results, gold, mostly free milling, 
being found plentifully throughout the deposits. A stamp mill is 
said to be treating the ore on the property since October 15. 


356 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

At the Supreme mine, operated by W. N. Harwood and associates, 
■which is located about 1,600 feet west-northwest of the Summit 
mine, at an elevation of 6,100 feet, the deposits occur in an 18-inch 
vein that dips 80° NNE. in rhyolite. The vein is composed mainly 
of a pale-brown iron-stained gangue of quartz, which has replaced 
rhyolite, and of silicified rhyolite. The croppings extend along the 
slope for several hundred feet and in the adjacent wall of High 
Grade Canyon are exposed for a vertical distance of over 100 feet. 

The vein when visited had been opened horizontally for 40 feet 
and to the depth of 30 feet. It apparently consists mainly of com¬ 
pletely silicified rhyolite or quartz. The walls, though well defined, 
are tight or frozen and without gangue, conditions which are not 
promising for continuity. The ore shows much free gold in wire 
and other forms. In some specimens the jagged wirelike forms pro¬ 
trude a twentieth of an inch above the surface of the weathered 
quartz. The gold is noticeably abundant in the quartz within half 
an inch of the less completely silicified rhyolite and in the darker 
varieties of the quartz. In places the vein for its full width is said to 
average $1,500 to the ton, and picked samples are said to range from 
$3,000 to $5,000 to the ton. 

Associated with the ore in places are pyrite and a little specularite 
in crystals about a fifth of an inch in diameter. A 5-ton test ship¬ 
ment is reported to have averaged $187 in gold and 12 ounces in 
silver to the ton. In places in the vein occur small stringers or lenses 
of apparently later milky-white quartz, with a few fresh feldspars. 
In these, however, no gold was found. 

Down the slope to the south, about 50 feet from the Supreme vein, 
is a similar vein, and 1,500 feet to the west-southwest, on the New 
Prince ground, are three parallel stringers or veins, of similar char¬ 
acter, from 12 to 14 inches in width. These veins as yet have re¬ 
ceived but little development. 

Recently (September, 1914) the Blowback claim, adjoining the 
Supreme mine on the south, is reported to have been worked and to 
have made a shipment of ore w T hich averaged $250 to the ton, nearly 
all in gold. 

Developments are also showing up well on the Flunky No. 2 claim, 
near by, which is reported to have just been acquired by the Lincoln 
Consolidated Co. for $37,500. It will be operated in conjunction 
with the company’s adjoining property, on which also extensive 
development work is being done. 

SOURCE OF THE LINCOLN HILL ORE DEPOSITS. 

The Lincoln Hill ore deposits examined in 1913, like those of 
Nenzel Hill and Packard, appear to have been formed chiefly by 
hydrothermal solutions, but pneumatolytic action seems also to have 


ROCHESTER MINING DISTRICT, NEV. 


357 


played an important part, as is attested by the presence of tour¬ 
maline in the veins. The process of formation was more of the 
nature of fissure filling with less replacement than in the Nenzel 
Hill deposits. 

South of Lincoln Hill, in the north slope of the ridge that bounds 
Rochester Canyon on the south, the deposits of the Buck and Charley 
mine, which was not visited, also occur in the rhyolite. They have 
produced upward of $10,000 worth of ore. 

In the lower tunnel of the mine, at a vertical depth of 200 feet, 
the vein is reported to carry a width of 4 to 15 feet of $18 ore with 
shoots 1 to 3 feet in width composed chiefly of ore averaging about 
$125 to the ton, mostly in gold. The mine is favorably situated for 
shipment, being directly on the line of the Nevada Short Line Rail¬ 
road, which is now being extended. 

In the northern part of the Lincoln Hill belt, in Limerick Canyon, 
are several prospects which were not visited. Among them is an 
opening on the Empire ground, on a quartz vein in greenstone. The 
quartz apparently in part has replaced barite and carries tetrahe- 
drite, a little stibnite, and molybdenite. 

Of the earlier workings in the Lincoln Hill belt the Oro Fino and 
Montezuma deserve passing notice. The Oro Fino mine, which was 
not visited, is situated about a mile northwest of Lincoln Hill, just 
across High Grade Canyon, on a southwest spur of Gold Ridge. A 
series of dumps suggested by their alignment that the vein belongs 
to the northwest system. It is thought by J. T. Reid to be on the 
same fissure or contact as the Humboldt Queen mine, 1 near the 
mouth of Limerick Canyon, described by Ransome. This fissure is 
held by some mining men to contain other promising prospects 
higher up in Limerick Canyon. 

According to reports, the Oro Fino mine in 1879 produced $58,000 
in high-grade gold ore, and in the early eighties it produced about 
200 tons of low-grade ore, averaging from $6 to $7 a ton, which was 
treated in a 5-stamp mill in the lower part of Limerick Canyon. 
Later Mr. Schmidt, of Ryepatch, is reported to have found in it a 
pocket of rich ore which yielded about $2,000. By some the mine is 
thought still to contain considerable workable ground. 

The old Montana shaft in Rochester Canyon, about a mile below 
Lincoln Hill, is on what appears to be a rhyolite dike dipping 
steeply west in the limestone of the Koipato formation. It is owned 
in New York. It was sunk in the early sixties and for a time pro¬ 
duced some high-grade ore. Since then it has not been productive. 
According to tests made by P. R. Whyttock, 2 the Montezuma and 
adjoining ground yield good assays. 


1 Ransome, F. L., op. cit., p. 33. 


2 Oral communication. 






358 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

DEPOSITS IN NEIGHBORING LOCALITIES. 

The discoveries made in Nenzel Hill and Lincoln Hill in 1912 and 
1913 naturally led to considerable prospecting in the surrounding 
hills, which resulted in a revival of activity at some of the old 
deposits and the discovery of some new ones. 

McILRAVY PROSPECT. 

About a mile northwest of Spring Valley Pass, and half a 
mile outside of the area mapped in Plate VIII, at an elevation of 
about 6,700 feet, is a deposit that differs from anything heretofore 
described in this report. It contains copper-silver ore in a barite- 
quartz gangue, barite having been apparently in part replaced by 
the quartz. The deposit occurs in the form of a bed, or bed vein, 
about a foot in width, which dips 25° SW., conformably with the 
general structure of the country rock, a dark greenstone (diorite 
porphyry?), and contains layers a few feet thick of a pale-green 
siliceous rock which is now a sericite-quartz schist but may have 
been originally rhyolite. 

The deposit occurs in or associated with one of these layers. It 
is opened mainly by a 30-foot incline. The ore minerals are azurite, 
malachite, chrysocolla, a little chalcopyrite, chalcocite, cerargyrite, 
and apparently some silver-bearing sulphantimonite. They occur 
associated, mainly in lenses and kidneys from 2 to 6 inches in width 
lying parallel with the walls of the vein. They are more or less 
interbanded or streaked with the barite-quartz gangue, with some 
dark-greenish micaceous mineral apparently belonging to the chlorite 
group, and with a dark-greenish mixture composed apparently of 
oxide of iron and manganese, with a little copper, pitchblende, and 
epidote. Some chalcopyrite also occurs in the vein. A considerable 
portion of the ore is said to average from 5 to 6 per cent in copper 
and $60 in silver to the ton. 

Northwest of the Mcllravy prospect the greenstone becomes dia- 
basic and extends into the mountains for the distance of a mile or 
more. It weathers in blocky forms which roughly resemble colum¬ 
nar structure, and for the first half mile or so beyond the Mcllravy 
prospect it contains numerous barite veins from 2 to 10 inches in 
width, dipping steeply northwest. Associated with the barite in the 
veins are some chloritic minerals. Some of the barite is coarsely 
crystalline. 

LEE-STUART MINE. 

Beyond the Mcllravy prospect, at the head of Spring Valley, 
about a mile and a half north-northwest of Spring Valley Pass, de¬ 
posits occur on the Lee-Stuart ground, which, at the time of the 


ROCHESTER MINING DISTRICT, NEV. 


359 


writer’s visit, were attracting attention through a strike made by 
a lessee named Carpenter. 

The deposits comprise three parallel veins or lodes, which are 
shown by croppings and openings to have a length of about a mile. 
They dip steeply northwest into the mountain and are spaced about 
1,600 feet apart horizontally and 500 feet apart vertically, the lowest 
vein being at an elevation of about 6,000 feet and easy of access. 
They are mineralogically similar to the deposits of Lincoln Hill, 
and apparently form the northward extension of that belt of min¬ 
eralization. 

These deposits lie in the porphyroid rocks of the Koipato forma¬ 
tion. The veins are approximately parallel with those of the main 
Nenzel Hill and Lincoln Hill system and seem to owe their position 
to the same system of sheeting or Assuring. In size and in their 
composite or lodelike character, the veins resemble the deposits of 
Nenzel Hill, though mineralogically they appear to be more like the 
Lincoln Hill type. The gangue is chiefly quartz with some silicified, 
altered, and replaced rhyolite or other rock, a portion of which may 
have been originally dike material. The quartz commonly contains 
needles and prisms of black tourmaline and rather large scales of 
specular hematite. The gold is free and coarse. 

The lower vein, on which most work has been done, is opened by 
an 800-foot tunnel, which is driven chiefly through greenstone and 
crosscuts the vein at about 400 feet in from the portal. Here the 
vein shows a width of 16 feet. It is composed mainly of a mixture 
of quartz and rhyolite containing free coarse gold. 

Near the southeast end of the vein, about 1,500 feet from the tunnel, 
are the Gold Dike and two other shallow shafts. The ore here shows 
considerable coarse free gold. Some particles are a fifth of an inch 
in diameter. 

The gold occurs chiefly in the quartz stringers and in the altered 
silicified porphyry within the lode, generally at or near the walls 
of the stringers. It occurs also in streaks of coarsely crystalline 
hematite that has apparently been derived from pyrite, and to some 
extent associated with fresh-looking black needles and prisms of 
tourmaline embedded in the quartz. Some of the hematite is very 
rich, the gold being contained in that mineral, with which, in places, 
is associated a little pyrrhotite. 

These Lee-Stuart veins apparently contain a large amount of gold, 
but owing to the sporadic distribution it is doubtful whether they 
are workable under present conditions. They were an important 
source of the gold mined in the Spring Valley placers, and they 
suggest that veins of their class were probably the chief source of 
the "gold found in the American Canyon placers. The ore of the 







360 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

middle vein is said to contain, besides gold, argentite and other sul¬ 
phides with some copper, and to be in part refractory. 

Near their western ends the veins are intersected diagonally by 
two east-west veins, which also carry some gold. Where they inter¬ 
sect the lower vein, a few hundred feet northeast of the Gold Dike 
shaft, they are about 80 feet apart and dip steeply north. 

Here, as at Lincoln Hill, the presence of tourmaline associated 
with the gold in the quartz indicates that pneumatolytic processes, 
as well as hydrothermal action, probably played an important part 
in the origin of the deposits, and the occurrence of the deposits and 
associated minerals toward the sides of the veins shows mineraliza¬ 
tion to have taken place chiefly during the early stages of fissure 
filling and vein formation. That some of the veins are altered dikes 
appears probable, but conclusive evidence of this has not been 
observed. 

COLE PROSPECT. 

At the time of the writer’s visit considerable interest was also mani¬ 
fested in cinnabar prospects in the surrounding region, and several 
newly discovered deposits were reported from the south end of the 
Star Peak Range. Most of these deposits are in the altered rhyo¬ 
litic rocks and are generally similar in their occurrence. 

The nearest of the prospects is in South American Canyon, about 
1J miles from Nenzel Hill. In this locality, on the east side of a 
gulch on the north side of the canyon, the cinnabar deposits are said 
to occur in three parallel northward-dipping veins in the rhyolite, one 
of which belongs to G. Cole, of Rochester. The entrance was locked 
at the time of the writer’s visit and the workings were not exam¬ 
ined. The deposits appear to be similar to those at the Dixie mine, 
next to be described, though apparently they are more extensive. 
The cinnabar, as seen in specimens, occurs as specks and small irregu¬ 
lar veinlets, the largest three-tenths of an inch in width, in the 
altered kaolinized rhyolite. Some of the mineral is well crystallized. 

DIXIE MINE. 

In American Canyon, about 2 miles northeast of Nenzel Hill and 
1| miles down the canyon, cinnabar has been known for some time 
at the Dixie mine and Nevada Almaclen prospects. These lode de¬ 
posits were discovered through the finding of particles and pebbles 
of cinnabar in the gold placers, and recently the United Placer Co. 
is said to have been organized for the purpose of resuming work on 
the gravels of American Canyon for cinnabar and gold. 

The Dixie mine is owned in Lovelock. Its deposit was described 
by Ransome 1 as a soft crushed kaolinized zone, at least 6 feet wide, 


1 Ransome, F. L., op. cit., p. 37. 





ROCHESTER MINING DISTRICT, NEV. 


361 


in porphyritic rhyolite, with little specks of cinnabar scattered 
through the kaolin. The zone, without exposed walls, dips into the 
hill at 15°-20° N. and is opened by an incline 200 feet long, with 
considerable drifting. 

At the time of the writer’s visit the incline had been sunk 200 feet 
deeper and additional drifts driven from it. Ore has been found all 
the way down, the cinnabar occurring in specks and small irregular 
bodies in the kaolinized rock. The ore is treated on the ground in 
a small mill and retort plant, which, it is said, produces quicksilver 
on a commercial scale from time to time. The ore is said to average 
about 2 per cent of metal. 1 

NEVADA ALMADEN PROSPECT. 

The Nevada Almaden prospect, owned by W. G. Adamson, of 
Winnemucca, which was not visited by the writer, is reported to be 
promising. The ore occurs in limestone with some eruptive rock 
forming the hanging wall. The vein is said to strike northwest and 
to dip 20° SW. Specimens shown to Mr. Ransome by Mr. Adamson 
“ contained abundant cinnabar in small irregular fissures in dark- 
gray limestone. The vein is said to have been traced for a length of 
3,500 feet and to have been opened to a maximum depth of 150 feet.” 2 

BUTTE PROSPECT. 

A cinnabar deposit, reported to be rich, was found in 1913 at Ante¬ 
lope Springs, about 8 miles south of Rochester, at the south end of 
the Star Peak Range. It is said to be just south of a low basalt- 
capped foothill butte. Like the neighboring Relief mine described 
further on, it is most easily reached from Lovelocks, about 18 miles 
to the west. It is said to occur in rhyolite in small bodies or irregu¬ 
lar veinlets and stringers as at the Cole prospect and the Dixie mine, 
near the contact of the rhyolite with limestone and to extend for 300 
yards in a north-south direction. 

McNICKLE PROSPECT. 

Another cinnabar deposit has been found about 4 miles south of 
Rochester, a mile south of the McNickle camp, at the west base of 
the range. It also occurs in altered rhyolite. 

All but one of the cinnabar deposits here described, in the southern 
end of the range, lie in a relatively narrow northeast-southwest 
belt, which for 9 miles follows the contact of the Koipato and Star 
Peak formations. The deposits apparently are all in the Star Peak 

1 McCaskey, H. D., Quicksilver : U. S. Geol. Survey Mineral Resources, 1909, pt. 1, pp. 
554-555, 1910. 

2 Ransome, F. L., loc. cit. 




362 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 


formation. Whether they have any genetic connection with this 
contact could not be determined in the brief time allotted to this 
work. 

It is worth noting that cinnabar is absent, so far as known, from 
the rocks of the Koipato formation, although in the Rochester dis¬ 
trict deposits in those rocks contain pyrite, chalcopyrite, barite, opal, 
and antimonial compounds, with which cinnabar is known to be 
elsewhere associated. The occurrence of the deposits in the Hum¬ 
boldt Range appears to be similar to that of the deposit near lone, 
on the west side of the Shoshone Range, described by McCaskey, 1 
where also the cinnabar occurs in rhyolite along one side only of a 
fault contact. 

RELIEF MINE. 

At the Relief mine, better known as the Old Relief mine, 4 miles 
south of Nenzel Hill, in the southern end of the range, the ore de¬ 
posits differ from anything thus far described in the Rochester dis¬ 
trict in that they occur in limestone and appear to belong to the 
general class of deposits that occur in the Star Peak Range and are 
described on page 338. 

The deposit was discovered in the early sixties and was worked 
mainly in the seventies. Current estimates of its production range 
from $200,000 to $2,500,000. Much of the ore produced was very 
rich and contained chiefly silver chloride with some bromide, and 
considerable native silver, some of which formed fine specimens. It 
apparently contained argentite also. According to J. T. Reid, 2 3 a 
carload of the ore shipped to Swansea, Wales, yielded $22,000. 

Afterward the mine was worked by the old Rochester Co., and 
still later by Bailey, who for a time took out much rich ore with large 
profits. Part of the ore was treated, by pan amalgamation, in a 
10-stamp mill built by the Rochester Co. near the mouth of Relief 
Canyon. This mill was removed in 1874. 

From 1898 to 1905 the mine was owned and worked by Mr. 
Hardesty, of Lovelocks, with fair results. It is now owned and 
operated by the Rochester Treasure Mining Co. (Inc.), of Lovelocks. 

The mine is near the head of Relief Canyon, which heads south of 
Buffalo Peak and opens southeastward into Black Knob Valley. It 
lies at an elevation of about 7,000 feet and is accessible by wagon 
road. 

The deposit is a quartz vein or lode, from 15 to 30 feet wide, in 
limestone. It dips about 55° W., though the limestone dips 40° SW. 
The limestone is dark gray, in thin to moderately thick beds, partly 
slaty, and has a thickness of 600 feet or more. It is underlain by 
light-colored rhyolite, with which it seems to be conformable, and is 

1 McCaskey, H. D., Quicksilver: U. S. Geol. Survey Mineral Resources, 1911, pt. 1, 

p. 908, 1912. 

3 Oral communication. 



ROCHESTER MINING DISTRICT, NEV. 


363 


overlain by a great thickness of dark-greenish, partly schistose ande¬ 
site, which appears to extend from the vicinity of the mine to the 
mouth of the canyon, 2 miles distant. The rhyolite is dense and 
consists chiefly of a microfelsitic to glassy base in which are a few 
small squeezed phenocrysts of quartz microcline and microperthite. 

These rocks all belong to the Star Peak formation. The contact 
of the limestone with the rhyolite is about 200 feet from the mine 
on the north, but no rhyolite has been cut in the workings. In the 
vicinity of the vein the limestone is in part silicified. 

The deposit is opened chiefly by tunnels and drifts for a horizontal 
distance of nearly 1,000 feet and through a vertical range of about 
320 feet. Croppings of quartz that has replaced calcite veinlets and 
limestone occur also 80 feet above the highest workings. 

According to report and observation, the vein is strong at nearly 
all places where it has been exposed, but the ore occurs mainly as 
pockets or disconnected bodies ranging in value from a thousand to 
several thousand dollars. The rich ore is said to be mostly on the 
hanging-wall side of the vein and that formerly stoped came mainly 
from the upper and middle levels. 

Work is now being done on the 200-foot or Blacksmith Shop level, 
which is at an elevation of about 7,000 feet and comprises several 
hundred feet of drifts. Access is gained to it through a 280-foot 
tunnel, which crosscuts the limestone and at a point 250 feet from the 
portal reaches the vein. At this place the vein is large and contains, 
besides stringers of quartz, considerable calcite and layers of lime¬ 
stone, all dipping 60° NW. The calcite and the limestone seem to 
be in part replaced by the quartz, which was introduced in solution 
with the ore minerals. The quartz in general is banded and contains 
some small vugs lined with druses of crystalline quartz. These vugs 
do not contain ore. A winze is being sunk on the ore body from 
this level. 

On a level about 100 feet lower, consisting of a 375-foot crosscut 
tunnel and a 30-foot drift on the vein, only gougelike material, some 
of it said to assay from $6 to $8 a ton, was found. 

The upper or 100-foot level, which is about 150 feet above the sec¬ 
ond level, is opened mainly by a 200-foot tunnel on the vein. The 
vein, for some distance from the portal, is 3 feet wide and consists 
of mottled ore. It carries on its hanging wall 6 inches of what 
appears to be reddish gouge. Farther in, however, this soft ma¬ 
terial becomes good ore, 2^ feet in width, and the ore body has here 
been stoped to a width of at least 5^ feet. Much of the high-grade 
ore extracted in early days came from this level. 

About 60 feet above the first or 100-foot level is a large open or 
daylight stope, which shows that the main part of the lode consists, 
for a width of 14 feet, of yellowish-brown crushed quartz, next to 







364 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

which, on the hanging-wall side, is 16 feet of rather siliceous min¬ 
eralized material, including some limestone, all more or less banded 
and dipping about 50° SSW. The deposit here contains also some 
crushed material suggestive of altered igneous rock. 

Although the quantity and character of ore in the lower workings, 
so far as learned, are not encouraging for deeper work, the mine ap¬ 
parently still contains considerable ore. It is also held by some that 
the old dumps, some of which are large, can be profitably milled. 

On the opposite side of Relief Canyon, about half a mile south 
of the Relief mine, and at a slightly lower elevation, is the Silver 
King mine, which was not visited. Its vein, in limestone, dips 
northwest and has been opened to a depth of 60 feet. It consists 
mainly of quartz and manganese oxide, roughly in the proportion 
of 2 to 1, and contains considerable ore, much of which ranges in 
tenor from $120 to $1,800 in silver and carries about a dollar in 
gold to the ton. The ore minerals are said to be chiefly silver bro¬ 
mide and chloride, with the bromide predominant. This property 
is also being worked on a small scale and is producing some ore. 

DEPOSITS IN POLE CANYON. 

At Pole Canyon, 6 miles northwest of Rochester and 5 miles north¬ 
east of Nixon, discoveries of ore were made at about the same time 
as at Rochester. 

At the time of the writer’s visit 18 miners were working in the 
camp, and 16 tons of ore had been taken out, averaging about $175 
to the ton. The ore came mostly from the Hunter, D'Armond, and 
Lowry leases. Some of it is very rich. The principal metals con¬ 
tained in the ore are gold, silver, and lead. 

The deposits occur at an elevation of about 6,000 feet, on the broad 
steep ridge that forms the south side of Pole Canyon. The topog¬ 
raphy is rugged and the canyon is deep, affording good exposures 
of the rocks. From the camp at the head of the wagon road in the 
canyon, at 5,200 feet elevation, the workings, half a mile distant, 
are reached by trail. A stream of good water flows through the 
canyon. 

The country rocks are rhyolite and dacite, belonging to the vol¬ 
canic complex of the Koipato formation, which apparently is rep¬ 
resented chiefly by the rhyolitic rocks eastward to the crest of the 
range. 

A few hundred feet west of the deposits the rhyolite is overlain, 
with steep dip to the west, by quartzite and this by medium to heavy 
bedded limestone, both apparently belonging to the Koipato forma¬ 
tion. A few hundred feet farther down the slope this limestone is 
overlain by a black limestone, 200 feet thick, belonging to the Star 
Peak formation, which in turn passes beneath a series of alternating 


ROCHESTER MINING DISTRICT, NEV. 


365 


gray and brown beds. As their dip decreases these beds pass be¬ 
neath the Quaternary sediments of Lake Lahontan. 

d he country rock of the deposits is porphyritic and some of it 
shows flow banding. It is traversed by a pronounced north-south 
sheeting, which has a steep dip to the west, and by numerous joints 
belonging to other systems. In consequence of these the rock readily 
separates into small fragments, many of which are less than an inch 
across. In places the rock 
is also profoundly sheared 
and has been rendered 
schistose, especially near 
veins and fault planes. 

On the north the rhyo¬ 
litic rocks and the deposits 
are cut off, as shown in fig¬ 
ure 92, by a dark green¬ 
stone schist, which appears 
to have been originally an 
intrusive igneous rock. The 
contact dips deeply to the 
southeast into the mountain. 

Dark, much crushed and 
sheared gougelike material, 
apparently derived from 
this rock, occurs locally on 
either wall of the adjoining 
veins. 

The deposits are valuable 
chiefly for gold and silver, 
but carry some lead. They 
comprise three approxi¬ 
mately parallel veins, from 
200 to 500 feet apart, in 
the rhyolite (fig. 92). They 
strike about N. 10° W. and dip 70° E. into the mountain, though in 
places the dip appears to decrease downward. They have a known 
length of 3,000 feet or more, and their outcrops show a vertical range 
of about 100 feet. They are well situated for working by a single 
crosscut tunnel. 

The veins range in width from a foot to 6 feet or more. The gangue 
is chiefly quartz, which not only has filled the original fissure, but has 
replaced the adjoining country rock for distances as great as 40 feet or 
more from the vein in some places. The veins and rock as a rule are 
hard and tight, but the vein is not u frozen ” to its walls. A distinct 
parting, in places hardly visible, separates the vein from the wall rock. 



Figure 92.—Plan and geologic relations of the prin 
cipal veins in the Pole Canyon district, Nev. 
























366 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 


The quartz in general is glassy. In part, it shows dark streaks of 
ore minerals and of partly replaced rhyolite. It contains many 
small cavities, in some of which free gold occurs, generally in close 
association with larger masses, apparently, of silver sulphide. The 
cavities, however, are not generally lined with secondary minerals, 
although fracture surfaces in the quartz are coated with pearly 
opaline silica, some of which is colored by iridescent hematite. 

The ore minerals are chiefly free native gold alloyed with some 
silver, pyrargyrite or some dark-reddish mineral of the ruby silver 
group, galena, and locally in the vugs a little fibrous cerusite. Asso¬ 
ciated with these minerals, but in general not abundant, are pyrite, 
arsenopyrite, hematite, and sphalerite. The pyrite and arsenopyrite 
are widely disseminated through the replacement quartz for 30 feet 
or more from the vein. 

Nearly all the ore shows free gold in rounded nugget-like particles, 
the largest of which are the size of a pin head. 

Most of the gold is of a pale brass or yellowish-white color, much 
lighter than the gold of Lincoln Hill or Spring Valley. Some of it 
is alloyed with about 50 per cent of silver and seems to be undoubtedly 
electrum. 

A microscopic section of the ore shows chiefly a gangue of medium 
to fine-grained crystalline quartz. Considerable sericite is present 
in places and a little fluorite, pyrite, and arsenopyrite. In this 
gangue the gold occupies very irregular interstices and fractures. In 
general, it is associated with and in part enveloped in a dark-reddish 
opaque mineral, which is probably pyrargyrite, though it was not 
determined owing to the difficulty of isolating it. It is probably an 
important source of the silver obtained from the ore. 

Three periods of silicification are recorded. The first preceded the 
deposition of the ore minerals. Crushing, followed by ore deposition, 
marked the second period, which probably was not sharply separated 
from the first. A third and less general silicification is indicated by 
veinlets of barren quartz. 

Where opened by the Hunter 30-foot shaft on the north end of the 
June No. 2 claim, the middle vein shows a width of 16 inches of 
partly banded or streaked gold-quartz ore of good grade. At another 
opening a few hundred feet to the south the ore carries also galena, 
considerable silver sulphide, and some arsenopyrite and pyrite. 

On the D’Armond lease, where opened by a shallow shaft, trench, 
and cut, the lower or west vein carries on the hanging wall side a 
shoot of rich gold-silver-lead ore 2 feet wide. This ore, which is 
banded, carries about 20 per cent lead, which occurs in the form of 
galena. 


ROCHESTER MINING DISTRICT, NEV. 367 

A few hundred feet to the south, on the Lowry lease and on the 
north end of the Blossom claim, the same vein is about 3 feet wide 
and has much green chloritic rock in the foot wall. 

The east or Hansen vein, where opened on the Wilson lease by a 
12-foot shaft and cut, has a width of 15 inches and is all good gold 
ore that contains some galena. Two tons of the ore, sacked on the 
dump, are said to average about $75 to the ton. 

At the Prince opening, 400 feet to the north, where the dip flattens 
to 35°, the vein is 8 feet wide and is composed chiefly of glassy quartz, 
containing a little hematite and sphalerite. 

AGE OF DEPOSITS OF THE ROCHESTER DISTRICT. 

From the close connection in origin of the deposits of the Hum¬ 
boldt Range with the folding and deformation of the Triassic and 
Jurassic rocks, Ransome 1 regards the deposits of the Humboldt 
Range as probably belonging to the early Cretaceous, like the gold 
veins of the Mother Lode belt in California. 

To this view the Rochester ore deposits seem in general to con¬ 
form. Their formation accompanied or followed the pronounced 
sheeting and jointing of the region. As regards origin they have 
been referred (p. 350) to the work of ascending hydrothermal mag¬ 
matic solutions. The nearest exposed mass of intrusive rock that 
appears adequate to account for these solutions is the considerable 
area of granite 7 miles to the north in Wrights Canyon, on the east 
slope of the range, which, as described on page 333, intrudes both the 
Koipato and Star Peak formations. 2 The time of this intrusion is 
shown to be at least post-Triassic and is regarded by Louderback 
as probably post-Jurassic. The ore deposits therefore belong to the 
same general period of intrusion as the batholiths of California 
and western Nevada, in connection with or following whose intrusion 
in sedimentary and other rocks ore deposits have been widely formed. 

In its southern extension the granite of the Wrights Canyon 
mass very likely underlies and intrudes the rocks in the Rochester 
area, for these batholithic intrusions are known to have taken place 
on a large scale. This view, as suggested by Jones, 3 is supported 
by the occurrence of tourmaline in the deposits of Lincoln Hill and 
Spring Valley, which mineral is as a rule closely associated with in¬ 
trusive granitic rocks. Moreover, granitoid material in the gravels 
of Walker Gulch, adjoining American Canyon, indicates the presence 
of granite in the near-by axial portion of the range. 


1 Ransome, F. L., op. cit., p. 46. 

2 Louderback, G. D., op. cit., pp. 317-318. 

3 Jones, J. C., loc. cit. 








368 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

The deposits accordingly appear to belong to the late Mesozoic 
metallogenetic epoch. 1 From the presence of tourmaline, arseno- 
pyrite, and other minerals commonly of deep-seated origin, it may 
be concluded that the deposits formed at considerable depth in what 
has been termed the deep-vein zone. 

FUTURE OF THE DISTRICT. 

From the deep-seated character of the deposits and their close 
association with the major geologic structures, which are shown to 
have been impressed upon the rocks of the region from the tops of 
the mountains to some distance below the floors of the deepest valleys, 
the deposits may reasonably be expected to extend to considerable 
depth. In the sulphide zone, however, they will probably become 
leaner and more regular in tenor than in the present workings, which 
are chiefly in the oxidized zone. 

PLACERS. 

AMERICAN CANYON. 

Placer mining was at one time an important industry in the south¬ 
ern end of the Star Peak Kange. Activity centered chiefly in Ameri¬ 
can Canyon and at Fitting in Spring Valley, 2 miles to the north. 
Early in the eighties these places contained flourishing placer camps. 
In American Canyon operations continued active until about 1895. 
Ransome 2 says: 

The placers were first worked by Americans, who are reported to have taken 
out gold to the value of about $1,000,000. The ground, however, soon passed 
into the possession of Chinese, who formed a considerable settlement in Ameri¬ 
can Canyon and mined the gravels with skill and assiduity by drifting from 
countless narrow shafts ranging from 40 to 85 feet deep. How much gold they 
obtained is unknown, but some estimates, doubtless much exaggerated, place the 
total at about $10,000,000. 

Under the Chinese system the ground, it is said, was subdivided 
into blocks 15 feet square. 

In American Canyon, at the time of the writer’s visit, two Chinese, 
the only inhabitants in the camp, working with a rocker, continued 
to win gold from the surface of the former rich diggings. After 
a heavy rain a few nuggets may still be picked up on the old dumps, 
but the ground is said to be almost worked out and was seemingly 
being abandoned. 

WALKER GULCH. 

In a parallel gulch, however, about half a mile north of American 
Canyon, at an elevation of about 4,700 feet, Mr. R. E. Walker, 


1 Lindgren, Waldemar, Metallogenetic epochs : Econ. Geology, vol. 4, pp. 415, 418, 1909. 
8 Ransome, F. L., op. cit., p. 12. 




ROCHESTER MIXING DISTRICT, NEV. 


3G9 


manager of the Dixie mine, has recently discovered what appear to 
be new and valuable deposits. These deposits underlie several hun¬ 
dred feet of basalt and apparently are the gravels of an ancient 
stream that flowed over Triassic limestone. These gravels are 
Tertiary or older. 

Where seen by the writer, at the east edge of the basalt, the deposits 
appear to extend without interruption beneath the basalt, which 
here forms a scarp, 10 to 12 feet high, across the channel. At the 
time of the writer’s visit, however, no excavation had been made to 
prove that the gravels extend under the basalt. About 100 feet east 
of the basalt a 60-foot shaft had been sunk in the deposits by Mr. 
Walker. This shaft shows that the deposits are similar to those 
worked in American Canyon except that the gravels are apparently 
more rounded and waterworn and contain considerable granitoid 
material. They are clearly fluviatile and are reported to show gold 
nearly all the way down in the shaft. At the bottom of the shaft is 
blue limestone, the surface of which slopes southward, toward the 
middle of the channel, the dip being 30°-40°. 

More recently Ernest G. Locke, 1 manager of the Lockslee Gold 
Placer Mining Co., which has purchased the deposits, reports that 
he has made a thorough exploration at different points and proved 
by excavations made beneath the basalt that the deposits, having a 
width of 500 feet and a length of half a mile, underlie the lava, 
which in places has baked and stained them red along the contact. 

South of the Walker shaft, at a point which was thought to be 
over the middle of the channel, Mr. Locke sank a 200-foot shaft 
without reaching bedrock. From the bottom of this shaft a cross¬ 
cut reached the north rim rock at 130 feet, and a 65-foot drift was 
run to the west parallel with the channel. With new machinery 
now being installed development work, it is said, will be continued 
to the bottom of the channel, where it is hoped the pay streak may 
be well defined. According to Ransome, 2 the Midas shaft, also sunk 
in American Canyon some years ago, is 200 feet deep and all in 
gravels and cla} 7 s. 

According to Mr. Locke, the gravels dip 30°-45° E. down the 
mountain side and seem to have been deposited by a stream flowing 
eastward into Buena Vista Valley, perhaps into Lake Lahontam 
which formerly occupied that valley. This comparatively steep 
dip may be due in part to orographic uplift since deposition. 

Like the Walker shaft, the Locke shaft is said to show gold from 
the surface down. The gold is coarse and the particles in general 
average about a fifth of a cent in value, though some were estimated 


1 Letter of Feb. 3, 1914. 

58849°—14-4 


2 Ransome, F. L., op. cit., p. 37. 




370 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

to have a value of a cent and a half. The gravels penetrated by 

the shaft are estimated by Mr. Locke to average from 75 cents to $1 

» 

to the cubic yard; those in the drift and the crosscut average some¬ 
what less. The gold is worth approximately $17 an ounce. 

The fact that the deposits in the drift and crosscut appear to 
average less than those penetrated in the shaft suggests that the gold 
may be concentrated at certain horizons, as in the deposits of Ameri¬ 
can Canyon, where the pay streaks were found at the depths of about 
40, 60, and 85 feet, respectively. 1 

Although the steep streamward slope of the rim rock may account 
for the fact that the gold is not concentrated on the bedrock thus 
far exposed, and although such a slope would strongly favor con¬ 
centration in the bottom of the channel, it should be remembered in 
formulating working plans that in American Canyon apparently 
no gold was taken from off the bedrock. 1 

SPRING VALLEY. 

At Spring Valley or Fitting, 3 miles northeast of Rochester, the 
Federal Mines Co.’s dredge, the only dredge operating in Nevada, is 
said to have had a very profitable season during the years 1913 and 
1914. In 1913 it worked chiefly in deposits that average about 224 
cents a cubic yard, but the excavations did not extend to bedrock. 
The last clean-up, made earl} 7 in June, 1914, is said to have shown a 
recovery of 30 cents to the cubic yard. The dredge is said to handle 
from 1,500 to 1,600 cubic yards a day with gasoline poAver. With 
electric power its capacity would be greatly increased. The gold 
bullion produced from these placers in 1911 ranged from 0.696 to 
0.730 fine. 2 


ROCHESTER CANYON. 

For many years it has been the custom of a feAv prospectors to 
procure their annual “ grub stake v from the gold placers in Roches¬ 
ter Canyon. Hardly any evidence of such work was observed, how¬ 
ever, in the writer's hasty trip through the canyon. At the time of 
the writer's visit, hoAvever, the graA T els were being exploited from 1 
to 2 miles below LoAver ToAvn, Avliere they are said to have a thick¬ 
ness of 85 feet and to yield fair prospects. They vary from 50 to 
seA^eral hundred feet or more in width. A shaft had been sunk 
through them to bedrock, and drifts were being run from the shaft 
to the rim rock. The bedrock here, as shown by material from the 
bottom of the shaft, is dark-purple quartzite. 


1 Ransome, F. L., loc. cit. 

2 Heikes, V. C., U. S. Geol. Survey Mineral Resources, 1911, pt. 1, p. 681, 1912. 




ROCHESTER MINING DISTRICT, NEV. 371 

The deposits consist of a heterogeneous mixture of the gulch 
gravels and finer detritus derived from the adjacent hill slopes. 
Their gold was doubtless derived through erosion from the lodes in 
Lincoln Hill and at the Limerick mine. 

WEAVER CANYON. 

\\ hether Weaver Canyon has been prospected for placers was not 
learned. If it has not, attention may be called to the fact that the 
unusually large quantity of gold contained in the ore of the Colligan 
and other mines at its head suggests that this canyon may be a good 
one to prospect. 


SOUTH AMERICAN CANYON. 

In South American Canyon, heading at the east base of Nenzei 
Hill, excavations show some work to have been done for placers but 
apparently not with good results. 


LIMERICK CANYON. 

Recently (April, 1914) placer gold has been discovered in the 
head of Limerick Canyon, in the south end of the Nenzei Hill min¬ 
eral belt, just north of the town of Panama at an elevation of about 
6,300 feet. The location, according to Mr. E. B. Mills, 1 superintend¬ 
ent of the Rochester Mines Co., who has kindly supplied the sub¬ 
stance of the following statement, is on a low ridge covered with 
sagebrush, and the gravel deposit extends about 6 feet in depth to 
bedrock. Two men with a rocker are said to take out from $60 to 
$100 a day. There seems to be no trace of the ledge or bedrock 
source of the gold in the vicinity. Later reports state that the sur¬ 
face overburden of 1 to 2 feet of the deposit is being removed by 
plow and scraper and the balance hauled to water for treatment. 

According to reports received in September, the deposits have an 
extent of nearly a mile. The pay gravel is from 12 to 15 inches thick 
and averages from $12 to $15 to the cubic yard. It lies on bedrock, 
where it appears to follow certain channels, and in places it is covered 
by 4 to 10 feet of overburden consisting of barren wash. Ten or 
twelve outfits are at work. Dry washing is being tried, it is said, 
with fair success, as the gold is mostly coarse. 

Special interest attaches to this deposit for several reasons. In the 
first place, it lies just over the range from the deposits of Walker 
Gulch, and the intervening area may contain lode deposits from 


1 Letter of Apr. 8, 1914. 



372 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 

which the placers on either side of the crest may have been derived. 
It should be prospected with care. In the second place, if the 
deposits are water-laid gravels, as they are said to be, they, like the 
deposits of Walker Gulch, apparently represent an ancient stream 
channel which may have crossed the range by way of Spring Valley 
Pass. This pass, now T the lowest in the range, has since been eroded 
to a slightly lower level and any gravel that it may have contained 
has been removed. In the third place, the occurrence of ancient 
auriferous channels so near the crest of the range suggests that they, 
too. may have been important contributors to the Spring Valley and 
American Canyon placers. 


o 





